Technical consultation on specifications and quality control of netting materials and mosquito nets
14-day continuous exposure to 54 °C, although a lower temperature may be applied for a longer time to products that are irreversibly damaged at 54 °C (testing at lower temperatures is unlikely to be necessary for untreated nets).
The rates of decline in bursting strength of currently available untreated netting materials are unknown. Anecdotal evidence, from field use, indicates that the strength of untreated polyester nets can decline to unacceptable levels within 2–3 years but this may be more due to “wear and tear” than to the simple effect of time. The meeting agreed that a minimum specification for storage stability may be required but that data are needed to ensure that the most appropriate characteristic is tested.
Manufacturers of untreated netting materials should provide data to WHO on the bursting strength of their products, before and after a test of storage stability at 54 °C for 2 weeks (CIPAC method MT 46.3), to support a future review of the need to test this characteristic and for setting appropriate limits.
A simple standard test of fabric durability should be developed, to predict the impact on bursting strength of 2 years “typical wear and tear”, involving a combination of washing, drying (shielded from direct sunlight) and storage at elevated temperature.