Have you spoken with food allergy experts (organizations like FARE, leading allergists)? This is not something where you want to be relying on information from a message board.
What if a baby is given an adult dose of epinephrine? What if people use this who have not been diagnosed by an allergist ... for example, maybe they have a food intolerance, or maybe they have a mental disability?
Unless you get this product backed by an organization like FARE, it does not sit well with me.
Add to the what ifs.....what if a person thinks it's anaphylaxis and it is not? What if they are having an anxiety attack?
It's one thing to take on that responsibility for yourself, your child, or a child in your care. But to be on a call list specifically to respond, I think as an individual you would have to take some responsibility if you gave the epi in error. Paramedics can check your pulse. Maybe fire/police can as well? But how many have the equipment in their home?
I have had anxiety attacks that closely resembled anaphylaxis. And it's not that uncommon. When ds was training he responded to an emergency call and the patient was positive he was having an anaphylactic reaction because of something he ate. He was wrong. And epi was the last thing he needed.
To answer your question, I'm not sure whether he sometimes stores his own bag, or always does. Sometimes he drives his own car, so he would have a bag for that. But, I'm not sure if he always keeps it, or just picks it up when he's got a job. Other times (for example working a kids football game) they want an ambulance on-site so he drives it, and the supplies would be in the ambulance. (The reason for wanting an on-site ambulance is to save the time of waiting for 9-1-1 to respond, especially if they are not close, and it's a high risk for injury.)