@six5532one I didn't remember to address this part of question: "can't imagine how the opened vial could get exposure to NTM if it's stored in a closed.."
Even though NTM infections are a hot topic for those of us with bronchiectasis because we're more susceptible to it than average and it's very difficult to treat, we're also more susceptible to more common bacteria, viruses and fungi that can cause respiratory infections. Those are often found on surfaces and are spread by our hands when we touch a contaminated surface and then our equipment. Reasonable precautions like handwashing and cleaning equipment, as we do, reduces that risk.