Technical consultation on specifications and quality control of netting materials and mosquito nets
strength is a much more useful and practical overall measurement. Poly- ethylene nets are commonly made of higher denier yarn than polyester nets. Denier should thus be specified in tendering and included on the label but it should not be part of routine quality testing.
4.5 Weight of netting material
For a specific product (e.g., warp-knitted polyester netting), the weight (grams per square metre) of the final netting material is closely linked to denier of the yarn and to mesh count. Lighter netting material is cheaper. Weight is not included in the minimum specification for netting materials but it should be stated on the packaging of the net. When appropriate, weight should be measured according to standard ISO 3801 (1977), with pre- conditioning according to ISO 139 (2005) (4 h, 20 ºC, 65% relative humidity).
4.6 Fire safety
Flammability of nets and netting depends on the polymer used to produce the yarn and the application or incorporation of any additives, including flame retardants. The potential for dripping of melting polymer at high tem- peratures is also an important characteristic, because of the risks to eyes and skin: it is related to the yarn polymer and does not change from net to net. Flammability may eventually be affected by insecticide treatment but there is no evidence so far supporting this hypothesis.
Polyester is a flammability Class 1 material (“non-flammable”) according to 16 CFR Part 1610. In a study on the flammability of netting materials, 10 samples of commercially available HDPE netting and 5 polyester samples were tested according to EN 1102 and 16 CFR Part 1610 (WHO, unpublished data). All samples were classified as non-flammable according to both standards. However, in a previous study of 8 samples of HDPE, 3 samples eventually ignited and dripped under EN 1102 conditions (“heterogeneous burn behaviour”), although all samples were classified as Class I (“non-flamma- ble”) according to 16 CFR part 1610.
Flammability should be determined by the manufacturer according to 16 CFR part 1610 but routine quality testing during procurement is not expected to be required.