In the case of indoor residual spraying (IRS), a special pesticide is systematically applied on the walls of a facility, using a special type of compression sprayer. Only a few types of pesticides and compression sprayers can be used for such an operation. Otherwise the walls can get stained. The advantage of indoor residual spraying is that it enables the walls of the facility to help with killing crawling and flying insects such as ants, mosquitoes and cockroaches that walk or perch on it. The