No. 3932 August 22, 1939 AIR CONDITIONING FOR THE RELIEF OF CEDAR-POLLEN HAYFEVER By Engineering Research Series No. 31 Bureau of Engineering Research The University of Texas Austin, Texas The benefits of education and of useful knowledge, generally diffused through a community, are essential to the preserva­tion of a free government. SAM HOUSTON Cultivated mind is the guardian genius of Democracy, and while guided and con­trolled by virtue, the noblest attribute of man. It is the only dictator that freemen acknowledge, and the only security which freemen desire. MIRABEAU B. LAMAR No. 3932: August 22, 1939 AIR CONDITIONING FOR THE RELIEF OF CEDAR-POLLEN HAYFEVER By ALVIN H. WILLIS Research Assistant and HOWARD E. DEGLER Professor of Mechanical Enl'ineering Engineering Research Series No. 31 Bureau of Engineering Research The University of Texas Austin, Texas THE UNIVERSITY OF TEXAS BUREAU OF ENGINEERING RESEARCH STAFF Homer Price Rainey_ ______________________________________________ President W. R. Woolrich________________________________________________________________ ____________Director and Dean of the College of Engineering Raymond F. Dawson____ Assistant Director-Testing Engineer H. E. Degler________________________________________ Mechanical Engineering S. P. Finch______________________________________________Civil Engineering Goldwin Goldsmith____________________________________________Architecture H. H. Power________________________________________Petroleum Engineering B. E. ShorL________________________________________Mechanical Engineering R. W. Warner________________________________________Electrical Engineering G. A~ Parkinson________________________.Assistant Testing Engineer A. H. Willis___________________________________________Research Assistant A. J. McCrocklin, Jr.__________________________Research Assistant COPYRIGHT. 1939 BY THE BOARD OF REGENTS OF THE UNIVERSITY OF TEXAS CONTENTS PAGE I. INTRODUCTION ------------------------------------------------------------5 General --------------------------------------------------------5 Object of Investigation_____________________________________________________ 6 Acknowledgments -----------------------------------------------------7 II. WEEDS, WASTE, AND HAYFEVER____________________________ 7 Winter and Early-spring Hayfever___________________________________ 8 Early-summer Hayfever -----------------------------------------------------8 Late-summer Hayfever ---------------------------------------------------8 Hayfever Due to Soil Abuses________________________________________ 12 Soil Recovery a Cure__________________________________________________________ 13 III. ALLERGY AND HYPERSENSITIVITY____________________________ 13 Allergy Defined -----------------------------------------------------------------13 Heredity ------------------------------------------------------------------------14 Natural and Acquired Sensitiveness____________________________________ 14 Agents which Tend to Sensitize Pollen ________________________________ 14 Animal Hair and Feathers_______________________________________ 15 Molds and Fungi________________________________________________________ 16 Insects ---------------------------------------------------------------------16 Dust ------------------------------------------------------------------16 Smoke -------------------------------------------------17 Bacteria ----------------------------------------------.-------17 Symptoms -------------------------------------------------------------17 Diagnosis -----------------------------------------------------------18 Treatment --------------------------------------------------------------------18 IV. AIR CONDITIONING AND ITS RELATION TO HAY­FEVER AS FOUND IN NORTHERN UNITED STATES ---------------------------------------------------------------------------19 Air Filtration for Relief_______________________________________________ 19 Limitations of Air Conditioning________________________________________ 21 V. BIOLOGICAL ASPECTS OF CEDAR-POLLEN HAY­FEVER ---------------------------------------------------------------------22 Cedar Pollen Causes Hayfever__________________________________________ 22 Irritation vs. Protein Theory_____________________________________________ 22 Cedar-pollen Distribution ____ -----------------------------------------------24 Hayfever Symptoms Mechanically Controlled_________________ 26 VI. TESTS OF COMMERCIAL MECHANICAL AIR-FIL­TERS FOR THEIR ABILITY TO REMOVE CEDAR POLLEN -----------------------------------------------------------------------27 Methods for Testing Filters _______________________________________________ 27 Air-sampling Device: lmpinger Apparatus_________________________ 30 Sampling Technique ------------------------------------------------------------33 Quantification of Impinger Sample__________________________________ 34 Procedure of Tests on Filters._____________________________________________ 35 Test Results on Commercial Mechanical Air-filters_______ 36 VII. AIR-CONDITIONING UNITS TO RELIEVE CEDAR­POLLEN HAYFEVER -----------------------------------------------40 Cooling Unit ----------------------------------------------------------40 Development of Fan-Filter-Heater Unit________________________ 41 Construction Details of The University of Texas Unit___ 41 VIII. CONCLUSIONS --------------------------------------------------------46 IX. BIBLIOGRAPHY -----------------------------47 ILLUSTRATIONS FIG. PAGE 1. Hayfever pollen areas for trees in the United States, winter and early spring -----------------------------------------------------------9 2. Hayfever pollen areas for grasses in the United States, summer ---------------------------------------------------------------------------------10 3. Hayfever pollen areas for weeds in the United States, late summer and fall_____________________________________________________________ 11 4. Dry cedar pollen, shriveled and rough, natural state_ _____________ 23 5. Moist cedar pollen with outer shell (exine) intact___________________ 24 6. Moist cedar pollen after outer shell (exine) has broken__________ 24 7. Cedar pollen cones on branch of a Texas cedar tree_______________ 25 8. Arrangement of apparatus and room for testing mechanical air filters ----------------------------------------------------------28 9. Details of flow chamber shown in Fig. 8--------------------------------------29 10. Air ejector and pollen-metering unit__________________________________________ 30 11. Vacuum pump (air-ejector type) for impinger apparatus______ 31 12. Greenburg-Smith impinger for collecting pollen in water_______ 32 13. Group "A" mechanical filters with renewable dry cellulose mats -------------------------------------------------------------------------36 14. Group "A" mechanical filters with renewable dry cellulose mats ----------------------------------------------------------------------36 15. Group "B" type of mechanical filter with glass fiber covered with an oily adhesive______________________________________________________ 37 16. Group "C" filter with dry woven glass-hair_________________________ 37 17. Group "D" mechanical filter with cardboard cellular con­ struction with an oil coating___________________________________________ 38 18. Group "E" filters with dry all-wool and part-wool felts_________ 39 19. The University of Texas fan-filter-heater unit with gas burner -------------------------------------------------------------------42 20. The University of Texas fan-filter-heater unit with electric heating coil --------------------------------------------------------------------43 21. The University of Texas fan-filter-heater unit with steam or hot water radiator__________________________________________________ 44 22. Photo of installed unit in a room of an Austin residence (indoors) --------------------------------------------------------------------------------45 23. Photo of installed unit in a room of an Austin residence (outdoors) ---------------------------------------------------------------46 AIR CONDITIONING FOR THE RELIEF OF CEDAR-POLLEN HAYFEVER Significant Results. Cedar-pollen hayfever, as expe­rienced by thousands of persons in Texas and Northern Mexico during the winter months, can be relieved by an air-conditioning unit costing less than $100. Cedar-pollen hayfever patients, in general, experience symptomatic re­ lief for the period during which they are confined to an air-cleaned room. The University of Texas unit as de­scribed in this bulletin was developed to accomplish the following basic functions: Supplying fresh aid from the outside to a room at a rate sufficient to build up a positive pressure in the room thus preventing inleakage of pollen­laden air; filtering the fresh air through a good quality filter thus removing all but traces of pollen; heating the filtered air before it is discharged into the room, because generally air at a low temperature with little pollen has the same effect on the patient as air at a high temperature heavily laden with pollen. Also presented is a discussion of the part that cedar pollen takes in causing hayfever, i.e., the irritation theory and the protein theory. I. INTRODUCTION General. There are now, 1939, about four million people in the United States who suffer from hayfever for a period of from two weeks to five months out of every year, unless they are protected by clinical immunization. From year to year there has been and most likely will continue to be a slow but persistent increase to this number. It has been said that we are more enlightened now than we were twenty years ago and that enlightenment leads to the proper diagnosis of more cases. Undoubtedly this is true, but it does not present the whole picture. The principal reason is that the weeds from which hayfever pollen is derived are increasing in abundance, with the result that the amount of pollen in the air is increasing, the number of those affected by it is increasing, and generally the severity of their affliction becomes greater year after year. Another contributing factor to the present day increased prevalance of hayfever is the changed living conditions of our people; fifty years ago agriculture provided a livelihood for most of our population and this healthful occupation seems to have immunized or built up a resistance in these people against hayfever, today most of our population live in urban centers and the sedentary lives of many people makes them more susceptible to illness, particularly to hayfever, than their ancestors. Object of Investigation. The present day prevalence of hayfever, as well as the ingenuity necessary to fight it, has aroused increased general interest. Quite naturally, this interest has turned to means for relieving and curing the hayfever sufferer. The medical profession has de­veloped several methods of treatment, serum injections, nasal sprays, removable nasal filters, etc., but experience has shown that in general relief can be obtained most logically by removing the cause. With this thought in mind the air conditioning engineer has been cooperating with the physician. A number of hayfever (pollen and dust) patients, in spite of all therapeutic efforts, fail to obtain adequate relief from distressing symptoms. Many hayfever victims in the cedar-pollen area find it advisable to travel several hundred miles to get out of the pollen area and obtain relief for the week-end or a longer period. During recent years attempts have been made to help these patients by employing mechanical equipment intended to provide room-air free from pollen and dust in their normal environment, home, factory, or office. The rapidly increasing number of persons afflicted with pollen (and dust) hayfever in this country has focused a good deal of interest on the further possibilities of mechan­ical air filters and electrostatic cleaners to insure improved health and increased efficiency of the American people, especially those who are gainfully employed. In some groups of workers the number of those susceptible to the cedar­pollen hayfever may be as high as 25 per cent. During the winter months (December to February) the pollen of the Texas cedars causes many cases of hayfever.1 It is the 1As to the discussion of the increase or decrease of the Texas cedars, we find some interesting facts. Some old settlers claim that years ago there were comparatively few cedar trees in Texas and that the Air Conditioning for the Relief of Cedar-Pollen Hay/ever purpose of this bulletin to acquaint its readers with the cedar-pollen hayfever problem, to discuss some of the work done along these lines, and to describe a simple low-cost air-conditioning unit that was developed to provide relief from cedar-pollen hayfever. The tests were conducted by the Bureau of Engineering Research at The University of Texas. Acknowledgments. The authors express their indebt­edness to Professor W. R. Woolrich, Dean of Engineering and Director of the Bureau of Engineering Research at The University of Texas for his timely suggestions and con­tinued encouragement; to Dr. W. W. Duke, former Pro­fessor of Experimental Medicine in the School of Medicine at the University of Kansas, for his discussion on "Allergy and Hypersensitivity"; and to Dr. R. P. Wodehouse, Yonkers, N.Y., and Natural History Magazine for the dis­cussion "Weeds, Waste, and Hayfever." The authors also wish to express their appreciation to the Texas State De­partment of Health for the use of their impinger (air­sampling) apparatus; to the air-filter manufacturers for supplying useful information and for the loan of filters that were used during these tests; and to the Department of Biology at The University of Texas for their cooperation in obtaining the necessary correlated biological information-; also to the librarians and other persons who provided in­formation and assistance that aided in the completion of this work. II. WEEDS, WASTE, AND HAYFEVER2 Hayfever generally occurs in three seasons, according to the flowering of the three classes of plants that cause it. hills were covered largely with high grass. This grassland was used for grazing; over-grazing without giving the land proper rest-periods probably gave the cedar growth a start. It then became common practice to burn the grass (and incidentally the cedar) off at definite intervals. As this area became more thickly populated fences were erected; over-grazing became more intense and the danger of burning the -fences stopped the practice of burning, until now many of the Texas hills are covered with a very thick growth of cedars. 2Material in this chapter taken from "Weeds, Waste, and Hay­fever" by R. P. Wodehouse, Natural History Magazine, March, 1939. Used by permission of Dr. Wodehouse and Natural History Magazine. During the winter and early spring hayfeyer may be caused by trees, during the early summer by grasses, and in late-summer months by weeds. Winter and Early-Spring Hayfever. One of the most important trees is the mountain cedar of Texas and Mexico, see area 1, Fig. 1. When it flowers, generally about Christ­mas time, it scatters great clouds of pollen, and sometimes the unsuspecting gather its greens for Christmas decora­tions. For this they are often rewarded with an attack of hayfever as the flowers, matured by the warm, dry air, fill the house with their pollen. In the early spring there are a few cases attributable to trees such as elms, oaks, birches, and poplars which flower very early, while still leafless. In the South and Southeast, see area 2, Fig. 1, where pecan trees are common their pollen claims more victims, as does that of the box elder in some cities of the Middle West and Rocky Mountain states. Early-Summer Hayfever. Virtually all the cases of early-summer hayfever in the Eastern states are due to the pollen of just five grasses: sweet vernal grass, June grass, orchard grass, timothy and red-top. In the South and West where the climate is too hot and dry for these grasses their places are taken by Bermuda grass and Johnson grass, see Fig. 2. These grasses flower in the late spring and early summer, starting soon after the trees have finished, and give rise to the type of hayfever commonly called "rose cold." It is astonishing that of the 1,100 or so different kinds of grass which are native or naturalized in the United States only seven are responsible for any considerable amount of hayfever; none of these seven hayfever grasses is native to America. The pollen of any grass can be irritating to the hayfever patient, yet all other grasses are negligible compared with these seven leaders. This is true because the others do not produce enough pollen. Late-Summer Hayfever. More than half of all the hay­fever in the United States occurs in late summer and is caused by the short and giant ragweeds, sagebrush, and Russian thistle (tumbleweed) ; these pollen areas are shown in Fig. 3. The victims (nearly three million) of ragweed hayfever are more numerous than those from all other -----...___ ~ ::i.. ---..... ·------..-·-.,.. ... I \ • ., : t ~ MONT. : N. o. c I I I i __ /-----------~MINN.' ~· j ---------, ' ,, o· f ] s.o. ! \, w1s. i:! • I \A• I I ' ;::I , •v Yo. , .---------~ ~ ·---------~,: ,..____ ­ I ' ' Q L---..----/ NE!!>. \ IOWA ,J -. ' ---..1--.., \ , ... : ' ...-------( \\..\... ~ I ~------------4. ' f COL. I ~ :::i::i I I t"'C> : : ~ --;...________ J --...... f --T-1-----0 ' f-----, ­ : : : ~ : N.M. : ~ I ~ t I ~ : ~ ~ ;::i i:l::: ~ ' I ~-''lt·'•Wl'f. ,:P!.\ Y;:ft y II ~ "'1 e \;; .\ ' .,,_;;· .....(....,... ·:,· :.,, ~ <:! ~ FIG. 1. Hayfever pollen areas for trees in the United States, winter and early spring. Used by permis-\0 sion of Natural History Magazine and Dr. R. P. Wodehouse. ,)}~ ;~LLEN AREAS )' INDICATED ~y ::.:· NUMERALS WITHIN LINES I Swutwrnalcya Z June orblue 9r.1ss •<;-/~FLA.~ ·;\ ~3 O~rd91"8$$ /,·:I ·'· 4 T1moth~ ·,: 5Redtopl> 6 &ennuc:la grass 7 .Jdinson gr.au ..... 0 ~ ~ ~· ;::: -~­0 ~ ~ 0­ .... ~­ c:;· ;:s FIG. 2. Hayfever pollen areas for grasses in the United States, summer. Used by permission of Natural History Magazine and Dr. R. P. Wodehouse. I I I I ·r-r-·-·-·-·---. ....., I ' l •••• r.___:I \ ') MONT. ' . I ,,.., ;,. \'--.. -~ ~-------- IOANo 1 f WYo. ----,-~~---: : : ··,· l--1--------.J__ I . I I I : .t. · I I f UTAN i ,L--------t------­ \ ,..., I ' I I " I 1'> I I / AA1z. J ' ,I I ·-._...I I FIG. 3. Hayfever pollen areas for weeds in the United States, late summer and fall. sion of Natural History Magazine and Dr. R. P. Wodehouse. POLLEN AREASI INDIC.ATEO l!>Y NUMERALS WITHIN LINES I 6i,,nt R119wee:d 2 Short Ragweed 3 Coast Sagebru 4 Sagebru:;h 5 Yeitern Walerlle1 6 Russian Thistle Used by permis­ i:I.. tj· ~ ~ ;::.· g· ~· 'O' .... ~ -~ ~ ~ ~ ~ f 0 ~ .... ...... ...... causes combined. In the Rocky Mountains and beyond, where the ragweeds are unimportant or absent, their place is taken by the sagebrushes, mugworts, and wormwoods, characteristic of the mountains, the Great Basin area, and the Pacific Coast, and by the salt bushes and oraches, char­acteristic of the Southwest; there are also other local plants too numerous to mention. Though all of these are native American plants, it is because of man's interference with nature's plan that they are growing in an unaccustomed abundance-hundred-inch plants at one-inch intervals. Though the Russian thistle (tumbleweed) is less than a century old in America, it is a pernicious weed and among the most important causes of hayfever in West Texas, also throughout the plains and prairies from the Mississippi River westward almost to the Pacific Ocean. Not actually a thistle, it is so called from its spine-tipped leaves. It is also called tumbleweed because in the fall of the year the plants break off from their roots and are rolled along the ground, distributing their seeds as they go. It is estimated that a single plant produces 20,000 to 30,000 seeds. Hayfever Due to Soil Abuses. There are other plants which contribute to the production of hayfever, but the seven grasses, the two ragweeds and the related false rag­weed and bur ragweed, the sagebrushes, mugworts and wormwoods, and tumbleweed account for most of it in North America that without them hayfever could be little more than a local phenomenon of academic interest. The seven grasses are useful agricultural plants when kept with­in bounds, causing most of their trouble when assuming the role of weeds. The others are ordinary weeds which, even apart from their hayfever proclivities, constitute a great national liability. Hayfever is nature's reply to man's destructive and wasteful exploitation of natural resources just as much as is soil erosion, wind erosion, and floods. It is less spec­tacular than great gullies carved out of hillsides by running water, or the disastrous dust storms that move whole farms into the next state, or the floods that sweep away bridges. These are nature's answer in her boisterous mood; in her more subtle mood the answer is hayfever, and it comes so softly that few of us suspect that it is the answer to our thoughtlessness or greed. Air Conditioning for the Relief of Cedar-Pollen Hay/ever 13 Soil Recovery a Cure. Some ultimate causes of hay­fever are: the destruction of the natural forest or cover of other vegetation, improper agriculture, the plowing of lands unsuited to agriculture and their subsequent abandonment, excessive grazing, and other processes destructive of our natural resources and often leading to soil erosion, but supposed to be inherent to Progress in America. Truly hayfever is a man-made disease, the by-product of a shift­less and unorganized advance of civilization. It has been said that only two types of landscape are tolerable, that left to itself and that brought completely under control. These are all we need for happiness. The correction of uneconomical misuses of the soil is strictly in accordance with the principles of land conservation, with the highest development of civilization, and with the great­est use of our continent. The best prevention of hayfever is to leave the land unmolested or to cultivate it properly and make it pay dividend$. Anything between means "weeds, waste, and hayfever." III. ALLERGY AND HYPERSENSITIVITY3 Allergy Defined. The person with allergy is an indi­vidual who inherits some peculiar constitutional make-up which causes him to become sensitive to certain things. Therefore these particular things become violently poison­ous to him, even when encountered in minute amounts. Allergy patients may become sensitive not only to material things but also to physical agents such as light, heat, or cold. Sensitiveness may develop to such an extreme in certain people that they may be affected by a millionth of a milligram of a substance which may be devoured as food by a nonsensitive person. Allergy is a real condition, its manifestations are grave. Whenever a person of allergic strain comes in intimate contact with an agent to which he is sensitive, he is certain to have a definite illness which may be mild, severe, or grave, depending upon the degree of contact. 3Material in this chapter was taken from "Allergy and Hyper­sensitivity" by Dr. W. W. Duke in the Modern Home Medical Adviser, edited by Morris Fishbein, M.D. Used by permission. The agents responsible for allergy are usually infinitesi­mal in size and inconspicuous. For this reason, a patient sensitive to a certain agent may be inclined falsely to blame his illness on something to which he is exposed simultaneously which he can see. For example, a person sen­sitive to the inconspicuous ragweed usually places the blame for his illness on some flowering plant blooming at the same time; for example, goldenrod, sunflower, or daisy. The fact is that goldenrod, sunflower, or daisy are practically never a cause of hayfever or asthma. A person sensitive to some fungus in house dust may blame for his illness, his wife. Heredity. Allergy is one of the most consistently hereditary of all diseases. If heredity comes from both sides of a family, the illness is likely to appear in the child at an early age. Since it appears that persons of allergic strain tend to intermarry, this is an important factor so far as the age of onset of the trouble is concerned. Where­as the allergic constitution is hereditary, different members of the same family may become sensitized to widely differ­ing substances. Natural and Acquired Sensitiveness. We are at a loss to know why one individual becomes sensitive to one foreign agent and others to another. It seems in many cases that an illness has something to do with it. For example, rather frequently a patient will date the onset of pollen disease from an attack of the measles, scarlet fever, pneumonia, or influenza. As a general rule people are most likely to become sensitive to something with which they are in inti­mate contact at frequent intervals and which they meet with in traces rather than in quantity, such, for example, as the common pollens of the environment in which they live, or dust material which they meet within their homes or places of business. Contact must have something to do with the development of sensitiveness, for Europeans were never found sensitive to American ragweed. Ragweed does not thrive in European countries. Agents Which Tend to Sensitize Pollen. Pollen is ap­parently the commonest of all causes of allergy. Symptoms caused by it are usually hayfever and asthma. Occasionally, it causes eczema of the hands and face and neck. In this Air Conditioning for the Reli.ef of Cedar-Pollen Hay/ever 15 case the oil of the plant can have the same effect, so that this type of eczema can occur during the summer months. Pollen cases usually give seasonal symptoms, in temper­ate climates occurring in the spring, summer, or fall. Cases which occur in the spring are caused, as a rule, by tree pollen which is set free in temperate climates between March and May. In southern climates, however, mountain cedar may pollinate during the winter months. Summer is the great grass season. In temperate climates, one or an­other of the grasses may pollinate between the middle of May and the middle or latter part of July. In southern climates, however, Bermuda grass may pollinate through­out a much longer season or even during the winter months. The weed season starts during the fall months, in the temperate climates between the first to the twenty-fifth of August and terminates, as a rule, with frost. Patients who have symptoms following the fall season which last through­out the winter months are, frequently, also sensitive to heat, cold, or to some object which they encounter during the winter months. The important pollens of a given district are the pollens of some tree, grass, or weed which grows in abundance and blooms inconspicuously, see Chapter II, "Weeds, Waste, and Hayfever." A flowering tree or grass or weed rarely causes trouble because of the fact that little pollen is produced by a flower and little escapes from the plant. Even the pollen of the corn is rarely carried far enough from the cornfield to affect people who do not live in the immediate vicinity of the growing corn. Animal Hair and Feathers. Sensitiveness to animal hair and feathers is an important cause of hayfever and asthma but is rarely to be compared with sensitiveness to pollen or foods. Patients may be sensitive to one or several ani­mals. They may be sensitive to the animal itself, its cured products, or both. The latter, however, is rare as compared with the former. Horse sensitiveness is the commonest type of animal sensitiveness. Less often there is sensitive­ness to cattle, sheep, hogs, dogs, cats, rabbits, or guinea pigs. Of the fowl, sensitiveness to chickens, ducks, geese, or pigeons is more common. Less common are sensitiveness to the cured products used in pillows and mattresses. Molds and Fungi. During the summer months, spores of fungi known as wheat rust or corn smut fill the air ; in fact, in quantity, frequently exceed grass pollen. Also, molds that grow on the leaves of trees and bushes are im­portant. One man was sensitive to a mold which grows on the bark of trees and was subject to unsightly eczema of the face and hands during the winter months owing to the escape of the spores from the bark of firewood. Certain molds that grow in houses in dry places, in rugs, curtains, and upholstery, are responsible, apparently, for hayfever and asthma in people who have trouble in certain houses but who are free from disturbance in other houses. Insects. Two types of allergy are caused by insects, one by the bite of the insects, the other by scales and hairs which are thrown off from insects of the moth and butterfly group. The former can cause violent general reaction, even death, as a result of one or several bites or stings of some particular variety of insect. The latter type (moth and butterfly) can cause hayfever, asthma, and eczema in cer­tain districts in which insects of this variety abound. This discovery is a recent important advance. The insects com­monly responsible for this type of allergy are inconspicuous in color and size. They can be observed above lawns at night during the summer months. if the lights from an automobile are cast across the lawn. They are found on the screens and around lights. Insects of the beetle and cockroach group are apparently unimportant in the rela­tionship to allergy. Dust. Patients can become sensitive to certain specific types of dust accumulating in certain places, especially in the dark corners of certain rooms, in curtains, upholstery, under the beds, and in carpets. This fact has proved most useful in the diagnosis and treatment of asthma, especially of the type called house asthma. The element in dust which is primarily responsible for this sort of illness probably varies. In one case it was proved definitely to be fungus. One patient who suffered from asthma constantly for eight years was proved sensitive to something which could be extracted from one rug. Her illness dated from the pur­chase of the rug, and she was cured completely by removal of the rug from the house. Air Conditioning for the Relief of Cedar-Pollen Hay/ever 17 Smoke. Certain people become sensitive to certain varieties of smoke ; wood smoke, coal smoke, tobacco smoke, cigarette smoke, or the smoke from burning leaves. This type of sensitiveness can be so specific that a person sensi­tive to cigarette smoke may tolerate cigar smoke. One patient was so sensitive to cigar smoke that the quantity carried home on the clothes of her husband at odd times would cause her to have asthma. Another patient highly sensitive to wood smoke could not live in houses with open fireplaces even though the fire was not burning. Apparently, enough of the fumes of wood smoke could be retained in the carpets and curtains and upholstery to cause her to have asthma. Bacteria. Apparently people can become sensitive to bacterial products and can have allergic symptoms due to absorption of bacterial products. Author's note: Other agents causing hayfever such as drugs, foods, plant oils, scratches, and serums can not be eliminated by the use of air conditioning, therefore they are not included in this discussion. Symptoms. General symptoms of allergy occur when­ever a sensitive patient encounters and absorbs an amount of some substance to which he is sensitive in quantity which is in excess of his tolerance. With the onset of a reaction of this type, a person usually feels a sense of itching followed frequently by redness of the skin or hives, and frequently sneezing, coughing, or asthma; also frequently nausea, vomiting, diarrhea, and prostration. The blood pressure usually falls, and the patient's pulse gets rapid or weak. The patient may lose consciousness, get blue and have convulsions. Puffiness and itching of the eyelids, slight redness of the lid margins, a tendency to tears and discomfort on exposure of eyes to light are frequent symptoms. Hayfever, sneez­ing, swelling of the membranes of the nose, nasal voice tones, excessive watery or clear secretion, and, in chronic cases, polyps affect the nose. Swelling of the lips and tongue, itching of the roof of the mouth, swelling of the soft palate, hoarseness, and a tendency to choke, are manifesta­tions in the mouth and throat. Asthma, chronic cough, spasmodic cough, shortness of breath on exertion, a tend­ency to wheeze on breathing, and expectoration of clear mucous sputum, are signs of difficulty in the lungs. The difficulty in breathing may reach extreme grades and make it impossible for the patient to get enough air to sustain life. Hives, swelling either general or local, itching of the skin, redness, eczema, increased secretion of moisture and grease, or dryness and scaling are reactions of the skin according to it~ sensitivity. Headache is a common symptom of allergy. It may be extreme, in fact, may torture a person almost into a state of unconsciousness. Allergic migraine is rela­tively common. Vaughan and Rowe believe food allergy is a common cause of migraine. Weakness, prostration, ner­vousness, trembling, convulsions, transitory paralysis, nii.mbness of the hands or feet, or dizziness, are various rrrades of reactions of the nervous system. Diagnosis. The discovery of the specific cause of allergy is often difficult. There is nothing in the practice of medicine which taxes the ingenuity, knowledge, and ex­perience of a physician as much as studying out an obscure case of allergy. Certain tests of the skin, eye, nose, and diet are useful in unraveling the allergy problem. Skin tests are truly valuable in the diagnosis of reactions caused by pollen, dander, flies, feathers, and molds, but are often hopelessly inadequate and misleading in the working out of food cases. Specific tests with cold, light, and scratches are likely to give accurate information if carried out ac­cording to indications given by the history of a case. Seasonal cases of hayfever, asthma, or eczema of the ex­posed parts are usually caused by pollen, fungi, or flies, occasionally by animals or plants, and rather frequently by heat, effort, cold, or light, and sometimes by a combination of two or more of these factors. When symptoms occur throughout the year, dust, foods, heat, effort, or cold, or some material encountered continually in homes or places of business, must be suspected. Careful diagnosis of the cause of allergy is essential to success in treatment. The patient, however, should not expect a complete diagnosis on his first or second visit to a physician. After one cause is found, others must be suspected. Treatment. There seem to be at least nine different types of allergy each of which needs to be treated according to its special indications. Most important in the treatment of allergy is a physician who understands the illness and who understands the patient. Hayfever, asthma, eczema, headache, or stomach trouble due to sensitivity can be treated along five lines, depending on the causes of the illness : 1. Avoidance or removal of specific cause of illness. 2. Avoidance or removal of con­tributory causes of illness. 3. Specific treatment with the agents responsible for the illness. 4. So-called nonspecific protein treatment. 5. Symptomatic treatment. Success in treatment depends primarily on a correct and complete diagnosis. Failure to obtain relief is almost always due to a wrong or incomplete diagnosis. It is to be noted that of the five methods offered above for treatment of hayfever the first and second can be ac­complished wholly by air conditioning and that air condi­tioning is an aid to the other three methods. The theories as to why the pollens and dusts, etc., cause hayfever are given in Chapter V, "Biological Aspects of Cedar-pollen Hayfever." IV. AIR CONDITIONING AND ITS RELATION TO HAYFEVER AS FOUND IN NORTHERN UNITED STATES Hayfever and asthma were long considered incurable diseases and the patients found relief only by the use of morphine or by travel to "Hayfever Resorts." For this reason physicians paid little attention to the sufferers and many of them became easy victims of quacks and sellers of patent medicines. Now through the ingenuity of the air conditioning engineer cooperating with the physician, this condition is being changed. The treatment of the "rich man's disease" as hayfever has been called is coming within the reach of everyone. Air Filtration for Relief. The old proven theory that the sufferer could be relieved by travel to a place having a pollen-free atmosphere is also the basis of this new relief. The only modification of this theory is that the traveling has been eliminated as pollen-free atmospheres can now be produced in the patient's home. This pollen-free atmosphere is available through the use of air-filtering devices. An idea of the success of these devices can be readily obtained from a short study of the experimental results of tests con­ducted on patients living in the Great Lakes and New England regions. The group of men who seem to have done the greatest amount of work along the line of Air Filtration for the Relief of Hayfever are T. Nelson, B. Z. Rappaport, and W. H. Welker. They published their experimental work in two papers ;4 these experiments were undertaken to de­termine the measure of relief that can be afforded the sufferer with uncomplicated hayfever by placing him in a room supplied with filtered air. They also desired to learn whether comparative freedom from pollen irritation for a portion of the twenty-four-hour period would establish reasonable personal efficiency for the remainder of the period. A study of the time element necessary to give relief from pollen asthma and the efficiency of the com­mercial apparatus for pollen removal was also included. The following conclusions from the second report on "Further Studies" by the above men gives a very good synopsis of the complete set of tests and results: 1. Ex­perimental and commercial filters as now manufactured are not 100 per cent efficient for removal of pollen. 2. Air filtration that removes all but traces of pollen will relieve symptoms of hayfever. 3. Symptoms reappear on exposure to pollen-laden air regardless of length of confinement to filtered air. The time for reappearance of symptoms is inversely proportional to the pollen concentration outdoors. 4. Filtered air, cooled from 8° to 10° F. below outside temperature without dehumidification, does not give as prompt or as great relief from symptoms of hayfever as uncooled filtered air. 5. If patients with pollen asthma are confined in filtered air for a sufficient length of time, their subjective symptoms of asthma will be relieved. The objective evidences of asthma disappear less readily. 6. The length of the primary confinement period in filtered air is determined by the severity of the asthma. 7. Pa­tients with asthma require a longer period of initial con­finement in filtered air than those with hayfever. 8. The tolerance period on exposure to pollen varies in the same 4"The Effect of Air Filtration on Hayfever and Pollen Asthma" (J.A.M.A. Vol. 98, pp. 1861, 1932) and "Further Studies" (J.A.M.A. Vol. 100, pp. 1935-92, 1933). individual from day to day because of the variation in the pollen concentration outdoors. 9. Confinement in filtered air before the onset of asthma will not prevent its occur­rence. 10. In addition to pollen concentration, weather changes are important influences in precipitation attacks of asthma in pollen sensitive patients. Limitations of Air Conditioning. Dr. C. P. Yaglou, De­partment of Industrial Hygiene, Harvard School of Public Health, sums up the practical side of the experiments up to 1937 in his discussion on the "Usefulness and Limita­tions of Air Conditioning Methods in the Control of Allergic Disorders." This was published as part of a paper on the "Application of Air Conditioning to the Treatment of Dis­ease" in Heating, Piping, and Air Conditioning Magazine, Vol. 9, p. 635, 1937. In this report he states that the results obtained with air filtration of the air-conditioning processes in the control of allergic conditions are fairly comparable to those obtained by desensitization treatment so long as the patients remain in the pollen-free atmosphere. But while specific desensitization is preventative and in a few instances curative for all practical purposes, filtration gives only temporary relief. With rare exception the symptoms recur on exposure to pollen-laden air. Moreover the useful­ness of air-conditioning methods is limited because all cases are not caused by air-borne substances. Cases of bacterial asthma do not respond at all to the treatment with filtered air. Despite these limitations, air conditioning methods possess definite advantages in simplicity and convenience, and under certain conditions provide almost immediate relief. Hayfever cases are usually relieved of most of their symptoms within an hour after exposure to properly fil­tered air. In pollen asthma cases relief comes more slowly, usually after an exposure of from 1 to 12 days depending upon the severity of the asthma. A pollen-free atmosphere is essentially valuable for pa­tients in whom desensitization has little or no relief, and in instances in which desensitization is not advisable owing to intercurrent illness. On the whole, air conditioning meth­ods are considered to be valuable adjuncts in medical diag­nosis and treatment of allergic disorders. V. BIOLOGICAL ASPECTS OF CEDAR-POLLEN HAYFEVER Cedar Pollen Causes Hayfever. Texas and the South­western area of the United States have a number of the pollen grasses causing the spring hayfever and the ragweed causing the autumn hayfever. Annually, however, in cer­tain parts of Texas there occurs a winter hayfever. Dr. S. N. Key of Austin, Texas, was apparently the first person to recognize the persistent "colds" of some of his patients as a form of hayfever.• The disease makes its appearance near the middle of December and lasts until the middle of February. Dr. Key with the assistance of Dr. Mary S. Young of the Department of Botany of The University of Texas, found that of the vegetation in this region, only "Juniperous Sabinoides," better known as Mountain, Mexi­can, or Rock Cedar and "Juniperous Virginiana" or Red Cedar flowered during the winter hayfever season. Ithas been said that before a given pollen can be accepted as the cause of hayfever it must satisfy the following con­ditions: 1. The pollen must contain the excitent of hay­fever. 2. The pollen must be anemophilous or wind-borne, as regards its mode of pollination. 3. The pollen must be produced in sufficiently large quantities. 4. The pollen must be sufficiently buoyant to be carried considerable distances. 5. The plant producing the pollen must be widely and abundantly distributed. From the following discussion it can readily be seen that the cedar pollen satisfies the above conditions and can be accepted as the cause of hayfever. Irritation vs. Protein Theory. The two theories that are generally accepted as reasons for pollen causing hay­fever are, first, the irritation theory and second, the protein theory. The irritation theory is that the pollen is rough or covered with spines, like a grass burr, that irritate the mucous membranes of the nose, throat, and lungs. The protein theory is one that was established about twenty­five years ago by animal experimentations, i.e., the blood of the allergic person is sensitive to certain proteins. Thus when pollen gets lodged in the nose, throat, or lungs of a •"The Etiology of Winter Hayfever in Texas," by Sam N. Key, M.D., Texas State Journal of Medicine, January, 1918. person allergic to that pollen, sufficient pollen protein is absorbed into the blood to cause hayfever. In Fig. 4 the dry pollen is shown; in this condition it is shriveled, rough, and dry. If it stayed in this condition it might readily cause irritation of the mucous membranes, but as this rough dry pollen comes in contact with the moisture of the nose, throat, or lungs it readily absorbs FIG. 4. Dry cedar pollen, shriveled and rough, natural state. large quantities of moisture. This absorption of moisture causes the dry shriveled pollen to swell and fill out into a full spherical condition without roughness or burrs of any kind, as shown in Fig. 5. When the pollen grain is allowed to absorb more moisture it swells until the outside shell (exine) breaks and is thrown off, the cell is seen to consist of the protoplast containing the nucleus or nuclei, sur­rounded by the intine which is thick, homogeneous, and transparent; the protoplast is principally protein and water. In this unprotected condition the protein is readily absorbed into the blood stream. The pollen is shown in this condition with the broken exine and its accompanying pollen cell in Fig. 6. Cedar-Pollen Distribution. The male cedar tree can be distinguished during the pollinating season by its brownish FIG. 5. Moist cedar pollen with outer shell (exine) intact. FIG. 6. Moist cedar pollen after outer shell ( exine) has broken. appearance caused by the innumerable small cones contain­ing pollen. The cones can be seen in Fig. 7 as they grow on the tip of each branchlet. The pollen grains produced in these cones are 18 to 20 microns in diameter when dry and 20 to 22 microns when moist but with the exine still intact. To obtain information as to the weight of these minute grains, the following method was used. A 0.1 gram of the FIG. 7. Cedar pollen cones on branch of a Texas cedar tree. pollen obtained from a cedar tree was placed in 175 cc. of fluid and shaken well. A 1 cc. sample of this fluid and its pollen suspension was placed in a Sedgwick-Rafter counting cell. To facilitate counting, the cell was then placed on a microscope (8 mm. x 20 hyplane eyepiece giving 420X) equipped with a mechanical stage and a "Whipple" ocular micrometer disk. The microscope thus equipped and cali­brated with a stage micrometer, gave a 0.35 mm. square counting field. The average count of 150 fields was 105 pollen grains per field. The counting cell being 50 mm. by 20 mm. and holding 1 cc. of solution gives 8,160 counting fields per cell or per cc. Thus with 0.1 gram of pollen in 175 cc., 8,160 fields per cc. and 105 pollen grains per field, there are about 150 million pollen grains per gram of pollen, or each pollen grain weighs l.46x10-11 pounds. Con­sidering the facts that one tree can produce several pounds of pollen and that the average wind velocity during the pollinating season is about 10 miles per hour, it is therefore not unusual that cedar-pollen hayfever is prevalent in a large part of the State of Texas. Another fact that leads to the large number of allergic cases is that the cedar grows abundantly in a region start­ing in the vicinity of Dallas and running west about 300 miles and south about 500 miles into the northern part of Mexico. The trees grow in large enough quantities in this region that they furnish the only means of support for many families through the production and sale of cedar posts. Hayfever Symptoms Mecha·nically Controlled. Tests were conducted in the laboratories of the Mechanical En­gineering Department of The University of Texas with two primary objects in view. First, will cedar pollen cause a person allergic to it to have hayfever out of season, and second, will air filtration have any effect on the hayfever patient? The preliminary tests consisted of placing several pa­tients in a test chamber at different times. By adding pollen to the air in the chamber (unknown to the patient) it was found that concentrations of 150 to 300 pollen grains per cu. ft. of air caused the patient to have the hayfever symptoms to a marked degree. The observer not being subject to hayfever was not affected at all. In each case after the patient showed an extreme condition of hayfever the air in the room was passed through a filter. Ten min­utes after the filtering was started a marked relief was noticeable in the patient's condition, and after a period of one hour practically all symptoms had passed away. These tests were so encouraging that it was decided to test sev­eral commercial filters for their ability to remove cedar pollen and subsequently to make recommendations as to the type of unit that would cheaply and efficiently remove the cedar pollen from the air. VI. TESTS OF COMMERCIAL MECHANICAL AIR­ FILTERS FOR THEIR ABILITY TO REMOVE CEDAR POLLEN The problem of filter testing is somewhat controversial. The primary reason seems to be that manufacturers fre­quently advertise their filters as being 98 to 99 per cent efficient whereas they may be only 50 to 60 per cent efficient. This variation is possibly due to the variety of test meth­ods, the types of dust used in the tests, and the method of calculation. The methods of test generally consist of plac­ing the filter in a fan and duct system that is so arranged that three primary operations can be made either simul­taneously or continuously during the time of test. These operations are first, injecting dust or other foreign material into the air stream before it passes the filter, second, sampling the air before it passes the filter, and third, sampling the air after it passes the filter. Methods for Testing Filters. Itis sufficient here to men­ tion the various methods for testing filters in the order of their merit. The first and most reliable method is the actual particle count, then in order are the Bureau of Standards blackness (color density) test, the weight method, and the adherence (particles adhere to oily sur­ face) method. The air-conditioned test chamber in the Mechanical En­ gineering Laboratory of The University of Texas offered a suitable place for conducting the tests on commercial me­ chanical filters for their ability to remove cedar pollen from the air. The fan and duct system was already equipped with the necessary air-measuring devices, and a small chamber that could be used as a mixing chamber. Figure 8 shows the general arrangement of the apparatus in the test chamber. The ceiling fan was a 36-in. Robbins and Myers fan and was used to prevent air stratification, to keep the pollen FIG. 8. Arrangement' of apparatus and room for testing mechanical air filters. from settling, and to insure a uniform pollen concentration. The air conditioning system included a spray chamber, room outlet and room inlet ducts, blower, and necessary dampers to control the air flow. The spray chamber was not used as a spray chamber but as a pollen mixing cham­ber. The room outlet duct was located near the floor in mid-position of the north wall. The room inlet duct dis­charged along the ceiling from the upper southeast corner of the room. The blower (Ilg, D-25 Universal Blower, 685 r.p.m.) under normal operating conditions with a filter and the rest of the system connected would deliver 1,000 c.f.m. to the room. This air flow was controlled to the desired discharge by means of a damper in the room outlet duct and was measured by a pitot tube in the room inlet duct. This pitot tube was connected to an Ellison inclined gage and was calibrated for the c.f.m. delivery. /ng . Air •: Wi l~-.J I, LH 1 I I 1 I l I: ~~-+..t-..:-_-:.-:.~=~~~~ I I I I i I I I I I I I I I I I I I I I I I I I I I I I I II I +--1-~--~~--r-~-rI I I I I I f I 1 I I I I I I I I II I I I I I I I I I I I I I I I I I ~=~=t=~=~=~=~=-:r..I I I I I I I I -d-:-:ci::L::~::-~::C-:..-=:.~:-=!_'i L------­ _o__..o.__ 1. 15"""---..i Patent Applied For t ~ (b ~ ;:;· ~ ~· ~ i "'Cl g. [ §' Pfifer ~-----_ .... _.,.. .,,. ..... ...... _.--­ ""'"'-----,, J. "'">..--_.... -/\·Blowar ~ ~ -------~ -;,.-_~, ---.... ---;:.---..,, P-1~ll I .... -I ---t" \ ,-'\""~;',1 -MoJ'or-, n _I '\--1-~--1 I I I "-'--r \ I I I I f I\ I -.! I --;.+--r --------,.......'-"""-.....--t---""j_..._ ....~-=---' ~ . --..-OuJ'.s1'7't1 Air r/lte~d Air - ~lit1~f•a' Air FAN, FILTER & HEATER UNIT (Eledric. Heater) Window ::ii.. tj• ~ lg: J "Q' ., ~ -~ !;• ~ ~ a. ~ r ~ :::t. ~ t Patent Applied For FIG. 20. The University of Texas fan-filter-heater air-conditioning unit with electric-heating coil. W/ndow i------.30'' 11 llB I Panel ~----------------­t------------------­r---------,I I I I t-------tr...............-a..."""-8"'~--~­f1 (J \ l., ~---~tr--------~~~~1. d hii'~t11 I t' ~ I I I I: I -----bk-------L-1.-!L ::::::::..---~---...:;-LJ Panel I Ouf/e-t-~r~I/ ·.-,~--Ill I I I I I I I I : 1 I 1 n n n ,-, n I I I I I I I I I I I I I I I I I I I I I : I :i I I I I I I I I I I I I I I I I I I I I I I I I II I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I I I I I I 1-1-+ -1.-'-1--T--1-,-1-.j. I l) 11 f I J l II 1-1 ~ -i t-1 ~-1 I I I I I I I I I I I I ~7.J.-J, ...H,_J--l_J.-.t_J.-4..-( N"-1--:--r-1--,-1--~-.,.--:--r-" "' ~/4fo~ ' -oepend3 on Radlalor­~ t ~ "' ~ ;:;· fV.sll-... ~ ~· ------, l ,, I R11 ~ ,, ..,,,,,. " II -Filtered Ali.. :I q 11 11 11 II f --H--/'leafed A/r i: l: ii 11 11 II ~ I 11 0­ 1I I 1 II .... 11 I II \I"\ 11 I I II l'I ~· FAN, FILTER!, HEATER ­ I:: 1: :: I . ~· UNIT 11 1: p Ii 11 II II 1,,Hot Water or Steam) II I1 ii II I I II ::::v:1 11 v \) I \I,-, I I j '~-~~-..../' kL>epend.s onRao'htor Patent Applied For FIG. 21. The University of Texas fan-filter-heater air-conditioning unit with steam or hot water radiator. As this unit supplies 100 per cent fresh air, some form of air heater is necessary. The type of heating system already in the room usually governs the type of heater to be used in the unit. It is possible to use gas, electricity, hot water, or steam. If gas is used care must be taken to prevent the flue gases from escaping into the room. The general shape Patent Applied For Fm. 22. Photo of installed unit in a room of an Austin residence (in­ doors). and arrangement of the various parts mentioned is gov­erned by the designer and the available materials. The experimental unit built by the authors was designed to be located in a window and use gas as a heating medium. The general layout and approximate dimensions are shown in Fig. 19. This unit was designed so that the fan and filter could be readily separated from the heater. Figures 20 and 21 show how this same fan and filter arrangement could be used with electricity, hot water, or steam as the heating medium. The frame was built of lxlxl/a in. angle iron and covered with No. 20-gauge sheet iron. The top cover is readily removable so that the filter can be replaced and the fan and motor can be serviced. Figures 22 and 23 show photographs (indoors and outdoors) of the unit as installed in a window of an Austin residence. Patent Applied For FIG. 23. Photo of installed unit in a room of an Austin residence (outdoors). VIII. CONCLUSIONS This bulletin describes some of the causes, effects, and methods of relief for hayfever, the ever-increasing man­made disease, which can be controlled only by a complete understanding of its significance and the subsequent coop­eration on the part of everyone. Hayfever is generally caused by pollen from trees, grasses, or weeds as found in ever-increasing quantities in all parts of the United States, but in some cases other allergic agents may be responsible. Modern sedentary occupations and urban concentration of population have undoubtedly contributed to the increase in the number of hayfever sufferers. Hayfever may be caused by irritation of the mucous membranes or by the absorption of the pollen proteins by the blood. Some persons build up an immunity (partial or whole) against "protein-type" hay­fever by out-of-season pollen-serum injections. Hayfever symptoms can be relieved most logically by re­moving the cause; controlled vegetation and an application of the principles of land conservation would help consider­ably in reducing the amount of pollen produced by trees, grasses, and weeds. Air filtration that removes all but traces of pollen will relieve symptoms of hayfever. In addi­tion to pollen concentrations, weather changes are impor­tant influences in precipitating attacks of hayfever in cedar­-pollen sensitive patients. Hayfever can be relieved by air conditioning methods which can be varied to meet seasonal requirements. The tests conducted by the Bureau of Engineering Re­search at The University of Texas show that cedar-pollen causes hayfever and that it may be relieved by mechanical means. These tests made possible the recommendation of an acceptable type of air filter for the purpose, also the design of a fan-filter-heater unit for the relief of cedar­pollen (winter) hayfever. The mechanical air filter recom­mended for use in this unit is a dry cellulose mat type of inexpensive and renewable construction in addition to being about 85 per cent efficient. These features combined with the simple construction of the complete unit make possible low manufacturing and low operating costs. The Univer­sity of Texas air-conditioning unit provides a possible means of relief to thousands of Texas citizens who are now suffering with cedar-pollen hayfever and its distressing symptoms. By replacing the heater with cooling coils, the unit could undoubtedly be adapted for the relief of hayfever caused by summer pollens. IX. BIBLIOGRAPHY "Allergic Diseases: Their Diagnosis and Treatment," by R. M. Bal­ yeat. Davis Company, 1938. "Pollen and Hayfever," by D. H. Campbell. Science, 1938; Vol. 87, p. 16. "Can Allergy Be Prevented?" by R. Chobot. Health Nursing, 1938; Vol. 30, p. 293. "Hayfever Plants of the Middle West," by Fassett, McGary & Bates. John Swift Co., 1938. "Control of Air-borne Organisms--Various Industrial Applications of Filters Reviewed," by H. C. Murphy. Heating, Piping, and Air Conditioning, 1938; Vol. 10, p. 384. "What Air Conditioning Engineers Should Know About Air Bac­teriology," by A. C. Stern. Heating and Ventilating, 1938; Vol. 35, pp. 15, 40, and 43. "Present Position of the Medical Aspects of Air Conditioning," by C. P. Yaglou. Heating and Ventilating, 1938; Vol. 35, p. 34. "Air Purification and Allergic Conditions," by E. M. Fraenkel. Pro­ceedings Royal, Society of Medicine, London, 1937; Vol. 30, p. 1547. "Hayfever Aided by Air-conditioning Unit," by F. H. Hodgson, Heat­ing and Ventilating, 1937; Vol. 34, p. 36. "Application of Air Conditioning to the Treatment of Disease," C. P. Yaglou. Heating, Piping, and Air Conditioning, 1937; Vol. 9, p. 635. "Air Cleaning as an Aid in the Treatment of Hayfever and Bronchial Asthma," by Criep and Green. J. Allergy, 1935-36, Vol. 7, pp. 120-33. "Hayfever Sufferers Relieved by Air Conditioning," by E. L. Mac­Quiddy. Heating and Ventilating, 1936; Vol. 33, p. 52. "Air Conditioning and Its Effect on Hayfever and Pollen Asthma,'' by W. H. Welker. Heating and Ventilating, 1936; Vol. 33, p. 37. "Pollen in Hayfever," by R. P. Wodehouse. Torreya, 1936; Vol. 36, p. 7. "The Pollen Content of the Air in North America," by 0. C. Durham. J. Allergy, 1935; Vol. 6, p. 128. "Air Conditioning in the Treatment of Pollen Asthma," by T. Nelson, and others. Heating, Piping, and Air Conditwning, 1934; Vol. 6, p. 329. "Observations of Hayfever Sufferers in Air-conditioned Room and the Relationship between the Pollen Content of Outdoor Air and Weather Conditions," by T. A. Kendall, and G. Weidner. Heating, Piping, and Air Conditioning, 1934; Vol. 6, p. 75. "The Treatment of Hayfever and Pollen Asthma by Air-conditioned Atmosphere," by L. N. Gray. Jour. A.M.A., 1933; Vol. 100, p. 1832. "The Effect of Air Filtration in Hayfever and Pollen Asthma, Further Studies," by Nelson, Rappaport, and Welker. Jour. A.M.A., 1933; Vol. 100, p. 1835. "Air Conditioning as a Means of Removing Pollen and Other Particu­late Matter and of Relieving Pollinosis," by Vaughan and Cooley. J. Allergy, 1933; Vol. 5, p. 37. "Filtered Air Relieves Hayfever," by Welker, Rappaport, and Nelson. Heating, Piping and Air Conditioning, 1933; Vol. 5, p. 348. "Plant Pollen-A Problem in Air Conditioning," by 0. C. Durham. Aerologist, 1932; Vol. 8, pp. 5-7. "Air Filter to Alleviate Hayfever," by B. Z. Rappaport. Sci. Am., 1932; Vol. 146, p. 105. "Filtered Air for Hayfever and Asthma Treatment," by F. C. Taylor. Heating and Ventilating, 1932; Vol. 29, p. 41. PUBLICATIONS OF THE BUREAU OF ENGINEERING *1. Bulletin No. 16. *2. Bulletin No. 164. *3. Bulletin No. 189. *4. Bulletin No. 362. *5. Bulletin No. 1. *6. Bulletin No. 26. 7. Bulletin No. 62. *8. Bulletin No. 65. *9. Bulletin No. 1725. 10. Bulletin No. 1733. 11. Bulletin No. 1735. *12. Bulletin No. 1752. *13. Bulletin No. 1759. 14. Bulletin No. 1771. *15. Bulletin No. 1814. *16. Bulletin No. 1815. *17. Bulletin No. 1839. 18. Bulletin No. 1855. 19. Bulletin No. 1922. 20. Bulletin No. 2215. *21. Bulletin No. 2439. 22. Bulletin No. 2712. 23. Bulletin No. 2730. :j:24. Bulletin No. 2813. 25. Bulletin No. 2814. 26. Bulletin No. 2825. 27. Bulletin No. 2922. 28. Bulletin No. 3114. 29. Bulletin No. 3128. 30. Bulletin No. 3819. 31. Bulletin No. 3932. RESEARCHt Rice Irrigation in Texas, by T. U. Taylor. 1902. The Austin Dam, by T. U. Taylor. 1910. The Composition of Coal and Lignite and the Use of Producer Gas in Texas, by W. B. Phillips, S. H. Worrell, and D. M. Phillips. 1911. Methods of Sewage Disposal for Texas Cities, by R. M. Jame­son. 1914. Annual Flow and Run-Off of Some Texas Streams, by T. U. Taylor. 1915. Street Paving in Texas, by E. T. Paxton. 1915. Road Materials of Texas, by J. P. Nash. 1915. Run-Off and Mean Flow of Some Texas Streams, by T. U. Taylor. 1915. Texas Granites, by J. P. Nash. 1917. Papers on Water Supply and Sanitation, by R. G. Tyler, Editor. 1917. Papers on Roads and Pavements, by R. G. Tyler, Editor, 1917. Boiler Waters: Their Chemical Composition, Use and Treat­ment, by W. T. Read. 1917. The Friction of Water in Pipes and Fittings, by F. E. Giesecke. 1917. Tests of Concrete Aggregates Used in Texas, by J. P. Nash. 1917. Chemical Analyses of Texas Rocks and Minerals, by E. P. Schoch. 1918. Physical Properties of Dense Concrete as Determined by the Relative Quantity of Cement, by F. E. Giesecke and S. P. Finch. 1918. Road Building Materials in Texas, by J. P. Nash, cooperation with C. L. Baker, E. L. Porch, and R. G. Tyler. 1918. The Strength of Fine-Aggregate Concrete, by F. E. Giesecke, H. R. Thomas, and G. A. Parkinson. 1918. Papers on Pavements Presented at Engineering Short Course~ by R. G. Tyler. 1919. Progress Report of the Engineering Research Division of the Bureau of Economic Geology and Technology, by F. E. Giesecke, H. R. Thomas, and G. A. Parkinson. 1922. Silting of the Lake at Austin, Texas, by T. U. Taylor. 1924. The Friction of Water in Elbows, by F. E. Giesecke, C. P. Reming, and J. W. Knudson. 1927. Effect of Various Salts in the Mixing Water on the Com­pressive Strength of Mortars, by F. E. Giesecke, H. R. Thomas, and G. A. Parkinson. 1927. Testing of Motor Vehicle Headlighting Devices and Investi­gation of Certain Phases of the Headlight Glare Problem, by C. R. Granberry. 1928. Effect of Physical Properties of Stone Used as Coarse Aggre­ gate on the Wear and Compressive Strength of Concrete, by H. R. Thomas and G. A. Parkinson. 1928. Preliminary Report on Relation between Strength of Port­land Cement Mortar and Its Temperature at Time of Test, by G. A. Parkinson, S. P. Finch, and J. E. Huff. 1928. A Study of Test Cylinders and Cores Taken from Concrete Roads in Texas During 1928, by J. A. Focht. 1929. A Method of Calculating the Performance of Vacuum Tube Circuits Used for the Plate Detection of Radio Signals, by J. P. Woods. 1931. Heat Transfer in a Commercial Heat Exchanger, by B. E. Short and M. M. Heller. 1931. Heat Transfer and Pressure Drop in Heat Exchangers, by Byron E. Short. 1938. Air Conditioning for the Relief of Cedar-Pollen Hayfever, by Alvin H. Willis and Howard E. Degler. 1939. t A limited number of copies of the bulletins not starred are available for free distribution. :j:By error printed as Bulletin No. 2831.