June 1%7 ET-239 United States Departraent of Agriculture Agricultural Research Administration Bureau of Bntomology and Plant Q^aarantine SWIMGING-SHUTTER APPARATUS FOR MEASURING SMALL DOSAGES OF INSECTICIDAL AEROSOL 1/ By E, R. KcGovran and J, H, Fales Division of Control Investigations Liquef ied-ges aeroaolg containing pyrethrum axe extremely toxic to mosquitoes (Stillivan, Goodhue, and Feles J), flies (McGovran, Fales, and Goodhue 6) and other flying insects. Tests with these aerosols must therefore be conducted in large rooms (Lindquist, Travis, Madden, Schroeder, and Jones U), or, if small rooms are used, precise measure- ments of very small quantities must "be made. The insects are often held in cages during the large-room testo, which procedure introduces a nuTiber of sources of error. If the insects are released in a large chamber, considerable time is required to collect them after a test, especially if they are still active, ©jad in addition a great deal of labor is needed to clean the insecticldal residue from the walls, ceiling, and floor, A Peet-Grady chamber ( 6 by 6 by 6 feet) is generally available in insecticide-testing laboratories. Such a chamber is large enough to permit notmal activity of the insects and dispersion of an aerosol cloud, and yet smsdl enough for the insects to be readily collected and the chamber cleaned between tests, Goodhue and Sullivan (_2_) published a drawing of p. laboratory apparatus for testing small amounts of aerosol, v;ith raodificetions and refinements a dosage of 0.25 gram was obtained with this apparatus, now called a pressure test tube dispenser. An improved model (Goodhue, Ballinger, and Fales 2) and another apparatus (Batt l) will produce a satisfactorllv dispensed minimiim dose of about 0,1 gram of aerosol. Even this small amount usxially kills all the mosquitoes in a Peet-Grady chamber, making corapai^ative tests against these insects impossible. In dispensing the entire content of a press'ore tube dispenser that holds a measured amount of aerosol delivery is constant at the maximum pressxia-e but varies at the beginning and the end of the discharge period. l/ This work was conducted under a transfer of funds, recommended by the Committee on Medical Research, from the Office of Scientific Research and Development to the Bureau of Entomology and Plant Quarantine, .2- Thf.B la of little Importance when large asotmts of aerosol are releaeed, but when the entire dotage Is released In a fraction of a second, the variation in delivery may materially change the average size of the aerosol drops. Unless the pressxire reaches a maximum in a fraction of a second and drops off very quickly, a considerable proportion of the aerosol will be discharged at pressures below the normal for practical applications. This paper describes an apparatus which was developed to dispense accurately measured small dosages of liquefledr^as aerosols into a Peet- Grady or smaller testing chamber. SWINGING-SHUTTER APPARATUS The apparatus developed is an application of the principle of a uniformly swinging shutter cutting the spray stream so that uniform deliveries during a fraction of a second can be obtained. The same principle has been applied In another manner in a roachr-testlng method (McGovran and Pales ^)* A cabinet containing the shutter, space for an aerosol dispenser, dispenser shut-off mechanism, and an exhaust fan is mounted on the side of a Peet>«Grady chamber (Pigs. 1 and 2)« A round hole, 1 inch in diameter, connects the cabinet with the chamber and is 8 Inches below the celling and 9 to 12 inches from one comer. This hole can be opened and closed by the shutter which swings like a pendulum. The stream of aerosol is dispersed against this shutter as it swings back and forth, permitting a given amount of aerosol to pass into the chamber. Variations in dosage can be obtained by chaziglng the number of swings of the shutter, the size of the opening in it, or the rate of discharge from the aerosol dispenser* Cabinet The cabinet is 3^ inches high, 20 inches wide, and 12 Inches deep (outside meastirements) , and made of wood with a nheetHnetal back. It is divided into three sections. The left rear corner of the cabinet may be made shallower than the remainder of the cabinet (Pig. l) in order to fit over the corner post of some Peet«-Grady chambers. The cabinet can be the same depth throughout where chamber construction permits (Pig. 2), The upper section is 18 1/2 Inches hlfh and has two glass doors. A removable rack, with an upright attached (Pig, 1, G, ejid Pig, 3)t securely holds the aerosol dispenser. The rack fits into a wooden stend on the floor of this section and is held in place with door buttons. The dispenser is mcanted on the stand with a metal clamp. The discharge tube la secured In a groove in the upright by heavy rubber bands. A 1-lnch hole it the metal back of the cabinet fits against a similar hole in the wall of the Feet-Grady chamber. This hole la onposite the tip of the discharge tube on the aerosol dispen- a«r (AK The top of the swinging shutter (b) , which operatea by nieanB of a "ball-hearing nr.otuitin^? (K) , extends over the hole. The weight (E) , and other apparatus to open and close the dispenser are also in this section. The middle section of the c£."binet is 11^ inches high and has one wooden door. This section hold^ sn exh^^ust fan ( I_) , and an air filter (H) consisting of e wooden frame and fovs layers of white flannel. The intake of the exhau^st fan is cohered with two layers of hea-v;*- flannel cloth. The fajti discharges outside the cahinet. The hall-hearing mounting (K) of the swinging shutter is in the hack of this section. The lower section of the cahinet is 8 l/k inches hi^h and open at the front. The lower end of the swinging shutter extends into this section. To the tip of the shutter is attached a lead hall ?. inches in diameter ( J) , which swings like s pendulum and assists in giving the shutter its \aniform motion, A frame on the floor of this section controls the amplitude of the swing. A hlock can he placed in this frame to hold the shutter in position. Swinging Shutter The swinging shutter (Pig. k) Is made of heavy sheet metal 26 inches lon^ end 7 inches wide, A 1-inch hole (a) through which the aerosol is delivered into the Peet-Grady chemher is 1/2 inch helow the top edge of the shutter, A 3-hy 3-.iDch metal plate with a slit in the center (B) fits over this hole to reduce the size of the opening. Along the edges of the slit are l/**-inch flanges extending at right angles from the plate, to prevent droplsts of insecticide that splash off the shutter from entering the spray stream end heing carried into the test chamter. The plate is attached to the shuttor with metal clips. By using plates with slits of different width the rate of discharge into the chsroher can he controlled. The axle (£), with hall hearing, supporting the shutter is attached to the metal hack of the cahinet. There i3 l/l6-inch clearance hetv/een the shutter and th^^ hack. Shut -off Apparatus This apparatus (Fig. 1, D, E, and F, and Fig. 5) is used to release the aerosol from an aerosol container into the closed cabinet. A rubber pad is pressed against the tip of the delivery tube to pre- vent the aerosol from being sprayed. This pad is a section of inner tube 1 inch square by I/8 inch thick, which is inserted in the grooves of a metal holder. This flat-backed metal holder is mounted tangen- tially on a horizontal round iron rod, which is bent at a 90° angle at its right end to form an L. Rotating the horizontal section of the rod through 180° presses the rubber against or removes it from the tip of the aerosol delivery tube ^^^H^rrBOA«> -A- The L-shaped rod (Fig. 1, D) is mounted in the upper section of the cabinet, the long arm extending across the back of the section just in front of the shutter and just below the opening into the chamber. There is a weight (Fig. 1, E) on the short arm of the rod. A piece of window sash cord (Fig. 1, F) is tied to this weight, thence up through the top of the cabinet over a pulley and down the outside where it can be fastened. When the cord is loosened the weight drops, turning the long arm so that the rubber covered metal plate pushes forward against the tip of the aerosol dispenser nozzle. The valve on the dispenser may then be opened but no aerosol escapes. Pulling the cord lifts the weight and turns the metal plate away from the nozzle tip and the aerosol begins discharging. It discharges into the cabi- net but not into the chamber xintil the shutter is swung. Exhaust Fan for Adjustment of Free sure in the Cabinet On the left outside well of the cabinet ia mounted a aanometer filled with heavj'' whHe petroleum oil. One end of the manoir5 ^» of aerosol solution per swing of the shutter. The following formula le used to determine dosages in milligrams per 1,000 cubic feet; 3.5xExHxU,63, in which H is the number of grams of aerosol delivered per second by the dispenser, N the number of swings of the shutter, U,63 the relation of the vol\me of the test chamber to 1,000 cubic feet, and 3«5 ^^* number of milligrams of aerosol delivered per swing when the dispenser delivers 1 gram of solution per second. Weighing the Aerosol To weigh the aerosol, a T-tube \^ich collected the aerosol was devised. Suction through this tube carrlad the aerosol-bearing air through filter paper, which removed the aerosol. The tube fitted over the l^inch opening into the Peet-Srady chamber. By weighing the tube before wid after discharge of the aerosol into it, the weight of the nonvolatile material could be determined. An aerosol solution con» talning 20 percent of nonvolatile solution was used. The shutter was swung often enough to give a deposit of approximately 100 b^. of non- volatile material in the T*-tube, As the material cooled rapidly at the point of discharge, not more than 1^ swings were made at one time. With this number of swing*, the maximum used in testing, no marked change in the temperature of the delivery tube was noted. After the period of discharge, 15 seconds or less, the dispenser was shut off and the shutter cleaned before additional swings were made, A series of flanged plates having openings of various widths were used. After numerous preliminary weighings, six weighings were made to determine the quantity of aerosol delivered through each plate. The delivery rates per l/l6 inch of opening in the flanged plate, if the aerosol was delivered at 1 gram per second, were as follows: Plate openings Total aerosol per 1/16 Total aerosol per (inches) inch of opening per plate 1 per swing swine (milligrams) 5.13 fmilllKrams^ 1 82.1 15/16 5.13 76.9 lVl6 5.13 71.8 13/16 5.13 66.7 12/16 A.87 58.it 11/16 A.S7 53.6 3/16 3.79 H.A -7- The average deviatiou from the average dosage for a single plate ranged from 0,08 percent to 1,17 percent for individual dosages. With R sufficiently wide selection of plates, and hy utilizing the correct opening and number of swings in the formula, any given dosage can "be obtained even though the rate of delivery of a dispeneer is high or low, I'or example, if a dosage of 80 mg. of total aerosol solution is desired and the dispenser delivers 0,73 gram per second, two swings with the ll/l6«>inch opening would give a dosage of 80.^ mg. Range of Dosage The swinging-shutter apparatus and procedure for quantitatively dispensing small dosages of liquefied-g as-generated aerosol can give a wide range of dosages. It is a micro method. 3.5 mg. of aerosol solution was delivered into the test chamber in a single swing, and the apparatus could be readily adjusted to deliver smaller amounts. With the largest opening through the shutter that was available, 32 mg. per swing was delivered. If large amounts are desired, 10 to 20 swings can be used for a single dose. This would give a dosage of 0.8 to 1.6 grams of aerosol solution. Literature Cited (1) Batt, G. H. 194-5. New sprayer for testing aerosols. Soap and Sanit. Chem. 21 (7): 117, 119. (2) Goodliue, L. D. , Ballinger, W. R. , and Fales, J. H. 1945. Improved dispenser for testing new liqu«fied-ga8 aerosols. Jour. Econ. Ent. 38: 709-710. (3) Goodhue, L. D. , and Sullivan, W. N. 19A2. The preparation of insecticidal aerosols by the use of liquefied gases. U. S. Bur. Ent. and Plant Quar. ET-190, 3 pp. (Processed.) (A) Lindquist, A. W. , Travis, B. V.^ Madden, A. H., and others 19A5. DDT euid pyrethrum aerosols to control mosquitoes and houseflies under semi-practical conditions. Jour. Econ. Ent. 38: 255-7. (5) McGovran, E. R. , and Fales, J. H. 19^. Roach testing. Soap and Sanit. Chem. 18 (3): 101, 103, 105, 107, and U7. (6) McGovran, E. R. , Fales, J. H., and Goodhue, L. D. 19A6. New formulations of aerosols dispersed by liquefied gases. Jour. Econ. Ent. 39: 216-219. (7) Sullivan, W. N., Goodhue, L. D. , and Fales, J. H. 19ii2. Toxicity to adult mosquitoes of aerosols produced by spraying solutions of insecticides in liquefied gas. Jour. Econ. Ent. 35: 48-51. 1 « +3 n ^ 0) 0) n ^ t 5 , pM -H o V r-l ►» rH o iH •o O 4^ O •» ed (« *:> J3 00 « u a b£ O Em s- •» « a> 0) (4 bdl ♦» m > OS <«— . (D ' <» » 09 ^ 43 c. u PH «Q <: o •H D 0 g. X*i o a txo m ■p •H CI •H O •H • -p TJ •g •P O Q| 03 C Q (^ 0 •H ^ O t3 o i~i € t^ ^ o L4 0 a fH a> U 4 o O » +» fc •H •6 05 tao « T3 x: ^«M ^ n 0) *^ ■p 0 O £ n 4J a ^ rj ed •♦-> 0} % « o 6 0 a f^ *3 «-< (^ U •H +J *3 5 +* (rt Ul 0 •H J3 (0 ^ 0 XI ♦3 ttf •H fM C ® TJ >* ^ § :3 ^ » 0 H O* El u ■P (d 4> 0) X ^< X! iH a H (H bj Cm) ■a o V4 ■H 9) •H •• 0 4^ iH a> §^ O 4J TJ •§ » t ^ a a> > •> bO « ca 8 •->l •H X ^ 0) « ••^ a n O 0) P« ^ ^<-s at I 43 a, fi ^ 4^ 09 O ••. "O d (4 «-) e Pi J3 •> fi (D Vi a o n a| o ^ o «) •• -P 3 T3 O to C ® U E4 C -P d -H jid ® a O -P M^ •<-» » B «) 3^4^ O 45 C ti ^ fl Pt P O Pi cd ^ •H O. 9 0,0 » r-4 a ou wn r-i o 9 BJ *^ 4) H «0 « CQ a) <^ «^ O ^ ^H oj ^ U, CO O ••>T3 Vi a> Pi O • P « fl a o ^ u x3 a o > 43 -H C o e ^a)ox>«)df94» ¥aopi»4>>.4a •H o 43 09 r-« r^ P W *-t t* 00. O •O » t3 p +3 ^i V^ SO * P4 ^ XJ « P« O O bO 3 M « o rio^ tf a 4:> «*; .* c £ -S "^ >, «cro 4^ B bp 3 I 3 X O -H M| ■ I .. n XI P 0) e 'O n «o p Pt So O O P« O.V. *-. 43 Figure 2, — Front view of cabinet with the doors open. Figure 3. — Dispenser mounted in top section of cabinet, -P O 43 « as -O -P O a> OS 01 o o Ot «> (h I 43 0) Vi * — _ ^ c X ^ « 4> P o. u o t>0 T -o oa © o _ 09 ^ 'O O O r^ «M P. o ^ I O 0) • ti *^ (D 00 O •2 25^ 0 4* '-^ * " fc o n •«^ a> c "'*" s a 43 d oj o ^ u x: Xi ai o cd ^ a) n ^ »< >» f43 O ^ ^ a o o d Cm 43 o q <1^ a> 43 d J- 0) TO 43 43 C ^ ^ (D g ^ o ^ 0) a> p M ^ d ^ J= o 1«Ug§43 0) C 43 O TO fl x: o ® 43 fl >» i>o « n o 0) q ^ ^g* a ax\ ■^.•> CO H I o t (0 • o 0) tjO o ^ Oi r-^ .0)43 C >H a H ';^ 0) 0) © t< D. a43 js ap O +3 -»3 af • © d H c^ -q •C « CJ „ '5 ^ +5 -H © C C t»0T3 J3 CO -H *4 C! .H 43 O ^ O * « ^4 X: C! nO 43 N © P •"H ^ XI o c <^ « TO tM S » O •^ © 0) 0| 00 X3 0< J3 jC CX To 43 43 ••^•H • . ti iH 43 W «^ 0) © O O U) o o 43 c r* -> 3 4j © fi-i © © x: e-« ^f ^ (0 Figure 6. — Position of operator when dispensing aerosol. Figure 7. — Rubber glove in side of cabinet for use in manipulating valve on commercial dispenser. UNIVERSITY OF FLORIDA 3 1262 09240 3863