The crosslinking of urethane polyols via isocyanates after the evaporation of the blowing agent reduces the amount of free polyisocyanate and diisocyanate, which migrates easily out of the blown urethane due to the high volatility of the isocyanates themselves.
You cannot "air out" these isocyanates as they are constantly present in decreasing amounts, until some time where the decrease in free isocyanate reaches trace levels because of complete crosslinking. You can "air out" a space to reduce the concentration of chemicals at a given time, but the chemicals will reappear in the space afterwards.
You must determine:
1. When the spray urethane foam insulation was sprayed. How long ago in days.
2. What the curing specifications are for that foam insulation itself.
Most likely the irritation you are feeling is due to free isocyanates migrating into the atmosphere, which are attemping to crosslink with your body chemistry. Your body responds with an immune response, which you seem to be describing.
What is curious is that free-isocyanate exposure has no known odor or taste. Therefore, it is unlikely that the taste you are experiencing has anything to do with free iso.
Low / very low ambient temperatures can drastically impede the cross-linking of isocyanates, which would dramatically increase the amount of free isocyanates due to extremely low reaction rates. Usually the cure schedules of spray foam insulation have minimum ambient temperatures specified for this very reason.
A more likely possibility associated with a "metallic taste" is inhalation of the smoke generated as the combustion by-products of polyurethane foam insulation . Is something burning the foam insulation? Have you been breathing smoke or welding fumes lately?
