The testo 810 simultaneously measures ambient air and surface temperature via infrared sensors, at the touch of a button. For example, the testo 810 thermometer can take the non-contact surface temperature of a radiator or air vent, and compare it with the air temperature of the room at the same time. The testo 810 features a 1-point laser sighting and 6:1 optics ratio; it's also very compact, convenient, and easy to operate.