Free Radon Test Kits for California Residents January is National Radon Action Month, and the cold winter months are the best time to test your home for radon. The California Indoor Radon Program is offering free test kits to households in California throughout the month of January, or until supplies run out. The kits are provided by the U.S. Environmental Protection Agency’s State Indoor Radon Grant fund, and are limited to one free test kit per household. Kits will arrive within 2-4 weeks of ordering. Additional test kits can be purchased through the our partner laboratory’s website for $8.45.