p.s. The employment laws in my State include any workplace of at least 15 employees.
IF the workplace "hazards" involve your protection from more than just co-workers and clients, some OSHA rules may also come into play to help boost your claim. All the best.

Hi Kat. You don't say what State you live but I assume your in the US. There are a lot of IFs in your question which make it hard to answer. Major companys are dealing with this very issue right now and there is no cookie-cutter answer. But in general, the employers have more rights than the workers. IF your employer requires you to return to the workplace and IF your COPD can be used as a medical accommodation, maybe your job will continue to allow telework for you. But nothing will require them to do so. They only have to protect you IN the workplace.
Of course you may be able to find dozens of other new careers that have switched to telework since the Pandemic and not have to put up much of a fight to protect your health.
Stay safe and be well.

Thanks. Helpful. In answer to RolandL's question, I'm in VA. And Jean, I do have a diagnosis based on the criteria you've stated as well as a physicians note with the diagnosis from my doctor and pulmonologist.

I think I'd go ahead and file a reasonable accommodation request that you be allowed to continue to work from home until it's considered safe to be inside without masks, and possibly even beyond that point. I'd make sure that your pulmonologist is on board with your request, because you may be asked to have them write some statement about your medical condition. A pulmonologist is going to have more clout as a specialist than your PCP. If you don't have a pulmonologist, you need to get one and be sure they've done the testing to confirm your COPD/emphysema diagnosis. Just FYI, if your PCP made the diagnosis without accompanying spirometry or Pulmonary Function Test results, it's not a definitive diagnosis. It's only a definitive diagnosis of COPD/emphysema if you've had the spirometry/ Pulmonary Function Test and been diagnosed by a pulmonologist. The HR department in your company will undoubtedly check.

The ADA requires employers with more than 50 people to accommodate such legitimate requests unless they are more costly than is reasonable for the employer. It would be more difficult for your employer to claim unreasonable costs for you working from home as you (and presumably many of your colleagues) are currently at home with their blessing. The only hitch is that you were working in the office with everyone else prior to COVID, so you'll need to describe when the end-point might be.