The effectiveness of these nets varies depending on the type of the net and how and where you use them. Nets impregnated with insecticides are proven to be extremely effective. But when it comes to window nets and door nets, they do not prevent the mosquitos completely. Moreover, if there are other openings in the wall or ceiling, they would be less useful. But still, they can reduce the number of flies that enter your house. In the case of bed nets, you have to keep them down always to prevent mosquitoes from getting inside the net. Otherwise, they too are not useful.