Again, effective flea control means treating your pet and your environment, including inside and outside your home. These products need to be used exactly as recommended. Read the instructions about the proper dilution and time frame regarding evaporation and inactivation before introducing pets back into these areas.
Organophosphates have a greater degree of toxicty and especially pose a threat to cats.
Cats are exquisitely sensititive to organophosphate products. Read labels carefully for specific information regarding safety precautions. You should focus your efforts on shaded areas where flea eggs and larvae hide. Open areas with direct sunlight exposure are inhospitable to fleas, however areas under outdoor carpeting, or furniture, under decks and tool sheds and especially areas where you pet sleeps are prime sources. It is also effective against ticks, spiders and cockroaches and has been shown to kill both adult and larval fleas for up to seven months.