Looking at the service manual and photos of the laptop, one can see that this laptop's fans exhaust hot air to the rear. They do not exhaust hot air up through the keyboard. It should be safe to use a keyboard cover. Always rest the laptop on a solid surface, not on a bed, couch, or your lap. The intake vents on the bottom must be unobstructed to bring in fresh air. 
Hello all, I recently purchased a Dell Precision 7670 laptop, and I was considering using a silicone keyboard cover. My only concern is that the cover may impede the laptop's ability to dissipate heat. Does anyone know if the new precision line vents heat through the keyboard gaps? If not, would it be safe to use a keyboard cover?   Appreciate all of your input.
Silicone Keyboard Cover (Heat dissipation)