BIG BLU needs very little introduction since it is used by nearly 80% of all HVAC Technicians throughout the U.S. Bubble leak detection was once considered gross and unreliable. To a certain degree it was true because the dominant makers of leak detector solutions relied on simple mixtures of soap and water . BIG BLU is a strong and persistent film forming liquid that has excelled in the field identification of gas leaks. It remains, the only bubble/foam indicator capable of detecting micro gas leakage down to 0.65 ounces per year. Non toxic, non corrosive, biodegradable and approved for use on Oxygen systems.