A 737 had a very slight haze through the cabin recently. It smelled like burning. Pilots turned back, haze dissipated. Shortly after landing several passengers and one of the pilots needed oxygen and were taken to hospital with migrains. They were crook for two days.
If I have had a fire I assume it created some sort of smoke and I have no idea how that smoke is going to effect my pax and crew in half an hours time. Land ASAP is my answer.