Do not flea bomb the house. In this day and age, there is simply no reason to ever have to use indiscriminate poisons again.
Imidacloprid is a chemical that will interupt the signals between the flea's brain and its autonomic system - its lungs and heart, etc. The lungs, heart and other internal organs cease to function. The flea drops dead within minutes. This chemical ONLY affects insects - fleas and ticks. It does NOTHING to mammals (cats & dogs)
There are several products that have this chemical in them as the main ingredient....
Frontline:
http://frontline.us.merial.com/products/index.aspAdvantage:
http://www.nofleas.com/How-Advantage-Works.aspIf your "Spot On" contains Imidacloprid, then there is no need to treat the house or the animals further. The treatment will last up to 3 months for cats and 1 month for dogs - even in the rain and when they swim. Fleas MUST feed. They try to feed on the cat or dog, but are killed within moments of hopping on board. They do not live to breed. Within a matter of weeks, as your dog and cat travel around the house, the flea population will cease to exist. If you live in an area that has a high flea population outside, the fleas will take a bit longer to erradicate, but they cannot come in on the animals - for they die if they try to ride the dog or cat.
If you wish to treat the house anyway, in addition to the topical treatment on the cat/dog, there is a product called X-O-Trol. This is a spray that you can spray on your carpets. It does not smell, and is relatively harmless to mammals/birds etc. It prevents flea eggs from hatching, kills the adults and prevents the larve from maturing to adulthood. One treatment will last a year. I would not use it with tiny kittens or puppies or very old, or ill animals, nor would I use it if you have a crawling child in the house but it is relatively benign and does a fantastic job. It is FAR less toxic than a flea bomb and you can control exactly where it goes. It will do a great job.
Flea bombs are old technology - and really do NOT do a good job. When you are done, you have to carefully clean EVERY surface in your home, from ceiling down to remove the residual poison. It is not healthy for you to live there is you fail to clean properly. Flea bombs have no residual kill, and will not kill eggs or larvae, nor can they kill fleas hidden in baseboards or that are on your animals.
Skip the flea bomb. Use the Topical, or a combination of topical and residual spray.