The current FDA certified propellant used in all metered dose inhalers in the USA is called HFA-134a or HFA-227. The HFA-134a is very similar to the refrigeration Freon that is sold for automobiles. The Medical propellant is controlled and not just anyone can buy it legally with certificates of authentication and traceability.
Because the cannabis industry is not regulated by anyone, it is possible for manufactures to short cut the system and use automotive Freon for the propellant in their inhalers. This is possibly the reason for the petroleum smell or taste. This is a guaranteed what to hurt someone.