BetterAir BA-500 Probiotic Refill bottle is easy to change and protects you from harmful contaminants and common allergens. High quality environmental probiotic to assure optimal purification and health benefits. Replace as needed or every 6 months under an average settings.BenefitsAutomatic and continuous cleaning of air ducts and HVAC componentsIncludes up to 6 months supply of Environmental Probiotics- 1 bottle Helps neutralize noxious odors from organic sourcesConsumes organic resources such as dust mite waste, pet dander, pollen and dead skin cellsReplenishes indoor spaces with beneficial probiotics to restore indoor ecological balanceCreates a protective shield on surfaces and inside shared objects to protect your personal space from irritants