Insect Killers- The chemicals in bug spray cover up the “scent” of carbon dioxide, so hunting insects can’t find you. Along with covering your scent, most bug sprays smell repulsive to bugs, which further dissuades them from coming near you. Raid Multi Insect Killer Odourless 300ml is a super-fast insecticide that keeps your home free of mosquitoes, flies and cockroaches. Mortein Energy Ball Multi Insect Killer Low Odour 300ml is formulated to effectively and quickly kill both flying and crawling insects.