Severe coughing in dogs

Question
My dog is nearly 21 years old, weighs 22.4 lbs and three months ago had a complete physical at the Michigna State school of veternarian medicine, trying to identify anatomical reasons for a severe cough.  He has been on Torbuteral and Pred for much of the past year since the coughing intensified, but they are now providing minimal help.  Since the does not cough when at the vets or clinics, I have begun to think about environmental contributing factors.  I've replaced mattresses, bedding, and carpeting is relatively new.  I have asked a contractor to inspect the house and he finds corroded copper sewar pipes in the crawl space need to be replace.  He suspects methane gas--although not detectable from an odor--may be circulating in the house.  In fact, whether coincidence or not, the dog's problems intensify at night when he sleeps in the bedrooms nearest the source of the problem.  Could methane gas be a relevant factor in the dog's condition?

Answer
Maybe you need to have your house checked for radon gas instead. It is colorless and odorless (methane is not odorless) and will cause severe lung problems in dogs and people both. It is a hidden killer.

New carpeting can also be a big problem because of the formaldehyde it is made with. It might not affect you as you are higher up but to a dog it is right in their face.

I developed asthma as a result of a new carpet like this- so that is possibly another cause.

You may have to rip those out and see. At 21 years of age I am surprised this isn't a heart condition causing this instead.