He is literally breathing smoke all day, and his system is so accustomed to it, anything else is irritating.
If he goes outside and walks briskly to the mailbox and back, I bet he coughs with the raw fresh air. I have a neighbor with similar lifestyle, smokes a lot in one room which she seldom leaves, and coughs whenever she isn't sitting on her couch.
He has to change it up. He should smoke even a few outside. I'm afraid he has other issues that really must be addressed. And by a professional. And yes, I'll say it. A psychologist and therapy. The boy needs some help, in my very humble opinion.
And I applaud you for trying to help your ex. And I really wish the both of you success.
You're right, he DOES cough more when he's not in his room... I never thought of that, the liquid just being an irritant because EVERYTHING's an irritant. Hmm... Well I have a few new flavors OTW from Johnsons Creek, lower nic than what I normally get and I've never ordered a premium juice like that. I'll let him try them on my new iTaste V3. Maybe if he finds a flavor he really likes, that could make all the difference. And yes, he does need psycho/spiritual help, badly. It makes me very sad, but I just don't see him ever going for it.
My concern was that the vapor may be worse for him than smoking, if it's not coming back out on exhale. And that the cough won't go away. Now that I've typed it, it sounds ridiculous tho. Unless he's allergic to something, I seriously doubt it could be worse than flaming tobacco. And I bet if cigarettes disappeared, he'd be vaping either til the cough stopped or in spite of it.
Have him take a big draw into his mouth and then open his mouth before inhaling. You will be able to see the vapor in his mouth if he has actually pulled some in. Not to be sneaky, but give him a dry empy ecig with the coil removed and have him draw on it. see if he coughs. Not to doubtfull, but that would prove wheather or not he's faking it.