Do you rest directly on the mat or use the cover or simply cover it with a sheet? I have read that if you want benefits from FIR you need the red lights directly against your skin?

The LEDs emit 660 nm monochromatic visible red light — this is different from far-infrared (FIR). For best results, the red lights should be in direct contact with the skin.

Only Purple Ereada® mats include the Photon (red-light) function together with FIR. Brown and Gemstone Ereada® mats provide FIR heat (and other functions), but they do not have red-light LEDs.

If you are using the mat for far-infrared heat, negative ions, or PEMF, you may use the included thin cover or the padded protector with the 3-D air-mesh layer. These layers help cushion the surface and improve comfort. You can also add towels or sheets if needed. As your body becomes accustomed to the pressure of the crystals, you may gradually remove the extra layers.

However, if you want to use the Purple Ereada® mat specifically for the red-light function, it is best to use it without covers so the light can reach the skin directly.