I may have discovered a cure for Dirty Sock Syndrome. This is that musty smell that occurs when a Cooling/Heating System first kicks on. It is not common, affects only 0.5 to 2% of homes, and is more prevalent in heat pump systems.
UPDATE: Pine-Sol "Commercial Solutions", in the 1.12 gallon size now has the necessary 8.7% Pine Oil (original product changed and does not). Should work well at 50% product/50% water concentration. Found it at Home Depot.
Use at your own risk. Use cleaning products only as directed by manufacturer. Protect eyes and skin.