Does a CPAP with humidification put MAC into the air?

I started using cpap about the same time I first started treatment for MAC, so I’ve given this a lot of thought over a few years. I don’t think anyone has done the studies to truly answer your question, but I doubt your husband's use of a cpap with humidifier would cause you any problem. What the cpap is putting out is going directly into his respiratory tract and being filtered by his nose and lungs before being released into the room air.
I sterilize the distilled water before putting it into the cpap reservoir since I’m the MAC person and I’m breathing it directly. I use a steripen (about $130 and still working fine after 2 years) in a glass of distilled water just before bed. It takes less than a minute. I doubt you need it, but it may be worth it to you for peace of mind and a good night's sleep for you both.

My pulmonologist at NJH told me to boil the distilled water for my Cpap. I boil a gallon at a time (for 11 minutes since I live close to sea level) and keep it in the refrigerator. I use that same boiled distilled water for my twice daily nasal rinses, so it lasts close to a week. Maybe that would make your husband more comfortable using his Cpap?

Thank you, those are great tips.