• The US Environmental Protection Administration (EPA) has issued rules related to conversions of petrol vehicles to CNG that are intended to (and will) make conversions easier and less expensive than full compliance requirements that have been in place for retrofit system suppliers since about 1994.
• Prior to 1994 gasoline vehicles were allowed by unofficial ‘administrative exemption’ to be converted without being considered to be ‘tampering’ by EPA. In 1994 regulations changed (at the request of the NGV advocates) and EPA began using a more serious certification process, which was in place since 1994 and became one reason NGV conversions were so expensive in the US.
• A three tier, aged-based system was established that was more flexible for NGV conversions of cars more than 2 years old yet still requires monitoring and compliance with EPA ‘relaxed’ requirements.
• Vehicles are classified as: new (less than 2 years olds); Intermediate age (two years up to ‘useful life’; and out of useful life (OUL) (not specified in years, but presumably 5-7 years)
• Requirements are to check on functionality of OBD system when operating on the alternative fuel instead of certification like OBD demonstration.