Vector and Pest Control in Refugee Situations (United Nations High Commissioner for Refugees (UNHCR) / Alto Comisionado de Naciones Unidas para los Refugiados (ACNUR), 1997, 124 p.): Annex 8. Calculation of the quantity and dilution of insecticide for use in impregnation of fabrics

Vector and Pest Control in Refugee Situations (United Nations High Commissioner for Refugees (UNHCR) / Alto Comisionado de Naciones Unidas para los Refugiados (ACNUR), 1997, 124 p.)

		(introduction...)
		Preface
		1. Introduction
		2. Factors influencing the spread of vectors in refugee camps
		3. Arthropods of medical importance
		4. Mosquitos
		5. Non-biting flies
		6. Lice
		7. Fleas
		8. Bed bugs
		9. Human scabies mites
		10. Ticks
		11. Other arthropods of medical importance
		12. Snails hosts of schistosomes
		13. Commensal rodents
		14. Organisation of a control programme
		15. Pesticides
		16. Safe use of insecticides
		Glossary
		Bibliographic selection
		Annex 1. Some arthropods and their importance to health
		Annex 2. Morphological characteristics of some arthropods of medical importance
		Annex 3. Reporting form for spraying operations
		Annex 4. Calculation of the quantity of solution and insecticide for use in treatments
		Annex 5. Determination of the insecticide concentration for use in a sprayer
		Annex 6. Preparation of a solution from an insecticide formulation
		Annex 7. Preparation of a solution from an emulsifiable concentrate
		Annex 8. Calculation of the quantity and dilution of insecticide for use in impregnation of fabrics
		Annex 9. Calculation of the quantity of molluscicide for use in a waterway

Annex 8. Calculation of the quantity and dilution of insecticide for use in impregnation of fabrics

In order to calculate the dilution of insecticide for use in impregnation of fabrics, the absorption capacity of the fabric per m² (which will vary according to its thickness and composition) has be taken into account.

The procedure is as follows:

(a) calculate the total surface area of the fabric to be impregnated;
(b) calculate the quantity of insecticide formulation required according to the following formula:

m² of fabric X g of a.i. per m² X 100
concentration (%) of the insecticide formulation

(c) calculate the absorption capacity by soaking the fabric or mosquito net in a basin containing a known quantity of water. Drain the fabric or net over the basin and measure the volume or weight of the water remaining in the basin;
(d) add the quantity of formulation (point (b)) to the quantity of water that was found to have impregnated the fabric after draining (point (c)).

Example:

To impregnate a 10 m² nylon mosquito net having a total absorption capacity of 500 ml water, using permethrin in a 50% emulsifiable concentrate at a dose of 0.5 g a.i. per m²:

10 ml of insecticide will, therefore, have to be mixed with 490 ml of water for each mosquito net (or 1 litre of insecticide with 50 litres of water for 100 mosquito nets).