Insecticide(s) for IRS are selected based on evidence of effectiveness and should have the following properties. They must:

• Kill more than 90% of the mosquitoes that make contact. Note, however, that mosquitoes can develop resistance to the insecticide used in IRS. If people in your community experience a high number of mosquito bites even if their houses are sprayed, or there are many mosquitoes resting inside sprayed houses, these could be early signs of resistance and should be reported to your supervisor.
• Remain effective at killing mosquitoes for a long time – that is, they must be long-lasting.
• Be safe for humans and domestic animals.
• Be acceptable to the community.