Our testers check electrical safety, measure surface temperatures, and carry out a tilt test. They also check which heaters continue heating when on their sides, as if they'd been knocked over.
With the heaters running at their highest heat setting, our testers drape a towel over the top, leaving any ventilation channels uncovered. A heater passes the test if it turns itself off or continues to heat without causing damage to itself or the towel. Most convection and column models pass this test, as did the ceramic fan heater. However radiant-and-convection models don't usually pass this test. Regardless of what type of heater it is, never drape anything over it and keep it clear of furnishings.