I have not had my hair dyed (I can't dare cover up those white hairs I love so much) :) but I have sat in one of those chairs for a long time and what I find is that since you can not really stretch or move around, if I sit there for over 30 min., it all depends on how I feel that moment. I will flare the next day, it could be from sitting at a baseball game, being in a long meeting or group, new or different smells have also caused flares for me. If the smell is bad it will hurt, if the smell is good, nothing happens. I wonder if you could explain your disability to the person dyeing your hair, ask them if you could stand or move around every 15 min or so for 5 to 10 min., they may object because it will take longer for them to finish you and move on to the next client, but the good ones will do it and not complain at all. Those are the ones that get my business, referrals, and bigger tips :) :) :)
I hope this helps, if it doesn't let me know and we will figure out something else :)