The answer is totally dependent on your severity of CFS.
And how intense it is when it flares.
Question: what is the probability of working outdoors on a hot humid day making the CFS flare faster than usual and you suddenly having brain fog while looking for the intersection to turn to get back to the campground after work?
In my case, my working indoors in stores days ended when my fatigue flares got so bad that I could not remember how the cash register, any cash register, worked and I was right in the middle of using it! And by that point I had been in and out of retail since the middle 1980s and I KNEW how cash registers worked.
Except now I didn't.
Also in my case, the fatigue can flare severe enough that I literally can not lift the hood of my minivan. Now, imagine similar happening to you while you are using a chainsaw ....