I live in south Florida, land of the fleas
after years of dog owning I can tell you that Borax really works. buy a box of Borax. Vacum your carpet and then use a strainer or flour sifter to spread Borax dust all over your carpet. It usually forms in to large hardened rocks in the box so a sifter or screen type strainer will help spread the dust evenly. Then take a broom and sweep the dust into the carpets. The fleas should be gone in about 48 hours. Re dust in two weeks and then every month. Eventually you will only need to reapply every six months. My pest control person told me that when they "fan for fleas" with a sprayer they are using Borax mixed with water.