I'm searching for some 2-4ft long 1-2ft wide heat mats to start plant seeds and cuttings on. In shopping around on Amazon I see that most (or all so far) heat mats have polarized 2-prong plugs. Shouldn't an electrical device designed to generate heat and be near water have a third, grounding prong?
Oddly enough most (also all so far) thermostats I've found specifically designed for plant heating mats have 3-prong outlets built onto them for mats to plug into, and the thermostat devices themselves have 3-prong plugs to go into a 3-prong (ideally GFCI) outlet.
Does anyone know the reason for this, or have any tips on where to find grounded heat mats for plants?