BAe 146 Airconditioning
 

An my last flight on a BAe 146-100 I noticed condensation ´steam´ coming from the upper air inlet openings only in the left aft fuselage (last two seat rows) during boarding and the first hour of flight, then it dissapeared. It was a sunny day with moderate temperature and low humidity.

How is the airconditioning/ventilation system in the 146 working ? Is there recirculation ? Where are the (or is the) air cycle machine installed ? Where is the air inlet located ? Where is fresh and recycled air mixed ? Are there some regions in the air ducting where water (I hope nothing else) can accumulate ?
Most interresting is not the condensation itself but the fact that it only happened in the aft left cabin and stopped after a while. Is the air quality in a 146 different in different parts of the cabin ? Should I choose a seat in a special area of the plane to prevent unhealty enviroment ?