Years ago, a major city hospital decided to do a change-out of its HVAC system. The specification for the replacement fluid was very loose - propylene glycol plus inhibitor. The contract went to a local home-brew supplier with the lowest bid, an oil jobber known for recycling propylene glycol from the local airport's aircraft deicing systems.
The HVAC system at the hospital was filled with approximately 3,500 gallons of diluted "PG plus inhibitor" solution. In a matter of days, all the joints and seals in the system started leaking. As reported in the local media, an odor of methylene chloride was detected in several areas of a hospital wing. After 24 staff members complained of flu-like symptoms, a common reaction to short-term methylene chloride exposure, 40 patients were evacuated.
How this contaminant came to be in the heat transfer fluid was never determined. It might have come from a dirty tank truck or it might have been in the fluid at the outset. Whether the propylene glycol was virgin fluid or recycled also remains a mystery.
After flushing out the system and repairing all the damaged joints and piping, the hospital contacted the local Dow distributor, who quickly rushed over a bulk shipment of 3,500 gallons of DOWFROST™ inhibited propylene glycol based fluid.
Like all Dow low-temperature heat transfer fluids, DOWFROST™ fluid is pure-quality, virgin fluid. Dow does not sell recycled glycol-based heat transfer fluids. Within a week of the original leaks, the DOWFROST™ solution was installed in the HVAC system. Dow has received no complaints from the hospital since.