Have friend who is asthma sufferer, who is bothered when A/C is on. Has split system - gas furnace and central air. Not bothered when heat is on or when unit is off. Someone suggested a sensitivity to mastic or possibly raw wood used to rebuild platform when unit was moved back on platform. Had electronic air cleaner and replaced that with a 4" media filter, but that does not take care of the problem as the filter is in the return and thinking the problem is beyond that. Measures taken so far before the idea that it might be the mastic are as follows: replaced the return ductwork, replaced the plenum and beyond, cleaned the coils, cleaned the ductwork and treated with a microbial agent, replaced electronic air cleaner with 4" media filter. UV light has been suggested. But they aren't keen on that idea as some UV lights emit ozone which is not good if you are sensitive to things, plus UV degrades plastic, your flex duct, wire coating, drain pan over time. Anyone have any other suggestions other than just moving?