I Have Asthma And Last Year After The Coil Was

I have asthma and last year after the coil was changed in the maintenance room I started to have very bad breathing problems. Went to emergency room and after 2.5 hours felt fine. I'm having an allergic reaction in my home. Did changing the coil have anything to do with it and what is the best filter for me. I had to turn off air conditioner when it happened and now am afraid to turn on heat.