Hercules® Megabubble® Leak Detector uses a high-viscosity formula that produces large, long-lastings blue bubbles for easier detection of even the smallest and slowest gas leaks on pipes, fittings, tanks, coils, cylinders, pressure vessels and valves. The formula is non-toxic, non-corrosive and will not freeze. Behold the power of Hercules®, products built to last and trusted by plumbers to withstand even the toughest conditions.