UV/IR filters reflect and block infrared rays (= heat). By attaching it in front of the lens of the camera CCD sensor or COMS sensor, ultraviolet rays and near-infrared rays that enter the inside of the body are blocked.
CCD sensors and COMS sensors are sensitive to wavelengths around 1100 nm, unlike the sensitivity of the human eyes, which does not detect light with wavelengths longer than 700 nm.