Experiments in practical culicidal fumigation / by Arthur I. Kendall.

  • Kendall, Arthur I.
Date:
1906
Catalogue details

Licence: In copyright

Credit: Experiments in practical culicidal fumigation / by Arthur I. Kendall. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    customary to enter thru one door only, which is protected by a curtain of heavy canvas to prevent the escape of insects. After the house is pasted up (which takes from one to several hours, depending upon the size and condition of the edifice), the pots contain- ing the fumigant are brought in; the amount of fumigant used in each pot and each compartment depends upon the size and shape of the area to be fumigated. As a rule, 2 pounds of sulfur or pyrethrum, the two most commonly used culicides, are allowed to each thousand cubic feet, and not more than 4 pounds are placed in a pot. This amount is chosen for several reasons; with smaller amounts per pot and a larger number of pots combustion is much quicker and usually more com- plete; a large amount of the culicidal substance is introduced in a com- paratively short time, and the loss by leakage, unless it is excessive, is met by the large volume of fumes which is generated in a minimal space of time. The sulfur or pyrethrum is lighted by methyl alcohol; a small amount is placed in each pot, in a small crater-shaped hollow made in the fumigant; this lights readily and starts the slower burn- ing sulfur without trouble. The time consumed in fumigating is usually about two or three hours. This allows ample time for the sulfur or pyrethrum to burn, and permits the fumes to diffuse thoroly thruout the building. At the expiration of the time allowed for the actual fumigation the house is opened, the. mosquitoes swept up with a damp broom, the paper and paste removed, and the house is once more ready for occupation. FACTORS INFLUENCING THE RESULTS OF FUMIGATION. Loss of active fumigating substance occurs by leakage, absorption, and condensation. Diffusion plays a very important part in the suc- cess of the operation as well. The penetration of a culicidal agent, considered apart from its dif- fusibility, is practically of no importance. Mosquitoes can not pene- trate the substance of fabrics or other furnishings, consequently, if the fumes diffuse sufficiently to envelop every article in the space which is being fumigated, the insects are almost certain to be affected. As a rule mosquitoes, as well as many other insects, show a remarkable tendency to hide in cracks and crevices where there is more or less intimate contact with the fresh uncontaminated air where the culicidal action is minimal. This is particularly the case with old houses in the Tropics, which are built for the maximum amount of ventilation, and where openings are not only not harmful but actually beneficial in so far as they facilitate the free entrance of air. Such edifices are extremely difficult to close tightly, and in such places one must use a culicide which has great killing powers. _ . As a rule, fortunately, structures presenting difficulties of this soit contain little or nothing which is actually damaged by sulfur dioxide, and it is customary to use sulfur under these conditions. The presence of large amounts of furniture, drapeiles, and hang- ino-s in general, which present a large amount of surface m proportion to~the space actually occupied, as well as offering hiding places for insects, seriously affect the results of fumigation. Not only is there loss of culicidal action due to poor diffusion, but the condensation of fumes on the surface of such fixtures results in further loss. Ordi- narily there is a certain amount of loss from this factor (condensation),