Just carrying gas does not equate needed to be HAZMAT certified. Thinking so is insane.
Do you know that the DOT requirements are anyone transporting less than 440lbs of hazardous materials and gas in containers of less than 8 gallons to have OSHA Hazard communication training and DOT materials of trade training as well as having a fire extinguisher? Or that if you have gas in a container between 8 gallons to 119 gallons only the level of DOT training goes up, no CDL? Or that shipping documents are required?
A few months ago I just went through HAZWOPR training again. Since HAZMAT and HAZWOPR overlap there's quite a bit of HAZMAT information. Everything above is in the book. A HAZMAT employee is someone who works for a HAZMAT employer.
A HAZMAT employer is a person (i) who
(I) employs or uses at least 1 hazmat employee on a full time, part time, or temporary basis; or
(II) is self-employed (including an owner-operator of a motor vehicle, vessel, or aircraft) transporting hazardous material in commerce; and
(ii) who
(I) transports hazardous material in commerce;
(II) causes hazardous material to be transported in commerce; or
(III) designs, manufactures, fabricates, inspects, marks, maintains, reconditions, repairs, or tests a package, container, or packaging component that is represented, marked, certified, or sold as qualified for use in transporting hazardous material in commerce; and
(B) includes a department, agency, or instrumentality of the United States Government, or an authority of a State, political subdivision of a State, or Indian tribe, carrying out an activity described in clause (ii).