I had this problem in apartments before. For you it is the HVAC system. For me, it was a shared wall.

I had tenants upstairs who smoked and all the tenants within our 4 apartment section shared a common wall for our laundry vents. My kitchen used to smell like an old ashtray. I complained to the manager, since she already knew I was allergic to smoke when I moved in and I had requested an apartment with new carpet and paint. She obliged me, since she had an apartment that was vacant and was already getting new carpet. What she didn’t realize was that sharing a common wall would make anyone elses air come into my apartment. When that tenant above me moved out, the landlord told me she would try to put a non-smoker there, but if she ran out of empty units other than that one, she’d have to allow smokers to move in. She had someone come in a few days later and asked her if there were any vacancies.The first question the landlord asked was “Do any of you smoke?” THEY LIED. She had other units these people could move into, and she would have let them have one if they hadn’t LIED. I was smelling smoke again but gave my neighbors the benefit of the doubt. Until I walked up to my apartment one morning at 9AM and saw my neighbor on the balcony directly above my apartment smoking and drinking a beer. I WAS LIVID. So was my landlord. But that wasn’t enough reason to kick them out, since it wasn’t in the contract they signed.

SO you can move. I’m sorry, but it’s obvious living around any neighbors who smoke will continue to make you sick. Maybe the landlord’s company has a duplex or small home you can rent. You should be able to get out of your lease for medical reasons.

Complain to the condo association and advise them of your health issues. Ask them to forbid smoking in common areas like the stairwell.

Check your local laws regarding smoking and if there is a violation, report it.

Try visiting a store like Home Depot to see if there is some type of filter you can install on the vents in your condo unit.

Unfortunately, I think your only other option is to move.

The cigarette smoke is coming from other residents: did you not notice it when you were house hunting? I imagine any remedies would be makeshift at best … perhaps you could purchase more efficient filter for your unit; perhaps you could purchase stand-alone air cleaners for the rooms in your unit. If you can’t find relief from the problem, check with a real estate lawyer … with asthma, your unit sounds unsafe for habitation and you may have remedies at law.