correct as Tom says you have to concider the insurance side of it.
eg, if i were to go on site and use my DOT bottle, it blows up and injures me and Tom who just happened to be stood next to me. First up my life insurance is not going to pay out because i was knowingly using a DOT bottle, also i would be liable to legal action from Tom, who if he was injured could quite legally sue me for his injuries.
its not worth it at the end of the day, if you have a DOT bottle throw the damn thing away and get a legal one.