ATLANTA (AP) -- A refrigerant called R22 has enjoyed widespread use for decades in the U.S. as an essential ingredient for residential air conditioners.But R22 harms the ozone layer and is being gradually phased out.The Environmental Protection Agency has issued a list of approved substitutes for R22, but cheaper, unapproved coolant has cropped up on the black market.The EPA says some substitutes for R22 could be flammable and pose a risk to homeowners and air conditioning technicians. So far, explosions have been rare.The FBI has issued a warning about the sale of flammable refrigerants and is conducting an investigation with the EPA.By PAMELA SAMPSONAssociated Press Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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