Generally speaking, the infrared rays emitted by the heat sources of fuel combustion and electric heating appliances are mostly near infrared rays. Because of their short wavelength, they produce a lot of thermal effects, which will cause skin burns and lens damage after long-term irradiation. Other electromagnetic waves with shorter wavelengths, such as ultraviolet rays, X-rays, and gamma rays, will dissociate electrons on atoms, which is more harmful to human body. On the other hand, the far infrared ray has a long wavelength and relatively low energy, so the danger of burning is relatively small when it is used.
Check the light source in the physiotherapy room.