I spray some HIT in my room. Then after 15-20 minutes, most mosquitoes tend to assemble near the tubelight. This is when I go for the final kill with an electric squatter.
From my personal experience with myself & my family members, i can say that these sprays do nothing else except for spoiling ur respiratory system. Mosquitoes become immune to it quickly, and u end up creating a mess of ur respiratory system. Better not use it. Especially if there r kids or old age members in ur home.