No Fun Flea Circus

Ring up Del and have him come over and collect his cat fleas.

And if he insists on charging for the service, only pay the flat rate and not the per-flea rate. Rumor has it he sprinkles pepper on the floor.

Put the cats in a different room each day and let them suck up the fleas and kill them. Then banish them back outside.

Then call in a cleaning service to clean up all the cat poop.

If no animals are inside won't the flea problem go away on it's own?

Use parafin and the fumes will make them go away.

If you use flea bombs, or flea sprays, use the type that is pyrethrin based. These are natural organics that come from the chrysanthemum flower. While no pesticide is completely safe, pyrethrins are somewhat safer than other types.

If the infestation isn't too bad, you could simply vacuum the area repeatedly. Put a flea collar in the vacuum bag (or canister) to help kill the fleas, and be sure to carry the vacuum outside when you need to empty it. Needless to say, wear long pants and a long sleeve shirt with rubber bands around the cuffs by your wrists and ankles.