Different nettings have different hole sizes. The size of the holes determines what size of insects are kept out and airflow and hence the temperature that the inside of the net reaches.
Hole size is a compromise between comfort and blocking insects. The larger the holes, the more breathable the net, thus the more comfortable, but larger holes mean that more insects can get through and bite you.
Smaller holes, while preventing almost all insects from penetrating to biting level, prevent air recycling, and are therefore much more clammy and hot to sleep in.

Some mosquito nets are treated with Permethrin to help enhance their protective qualities. Permethrin is a naturally found insecticide with an excellent safety record and has been used for decades.
Permethrin treatment is recommended by the World Health Organisation and has three key benefits: it reduces the number of insects within a room (and hence risk of bites and disease), it deters insects from biting through the netting, it helps protect damaged or poorly erected nets.
Each treatment lasts approximately 6 months depending on net storage and use, and, using the SafariQuip re-treatment kit, you can ensure your Mosquito Net is always protecting you.

Mosquito Netting is usually made from polyamide (nylon), polyester (terylene) or cotton.
Cotton is not widely used now on account of low tear stength and low resistance to damp and mould. Despite this, cotton, due to the "hairy" nature of cotton thread, works well at blocking insects and is very resistant to degradation by UV (sunlight).
Polyamide and polyester nets are the most common net material nowadays having very high strengths, low weight and high resistance to damp or humid conditions.
Recently, nets from monofilament threads have begun to appear on the market. These are cheap to produce but have a lot of disadvantages and are not recommended. The net structure is easily damaged and distorted making irregular and potentially insect large holes, also they do not hold permethrin treatment well. They can be recognised by an appearance similar to knitted fishing line.