You can block it. The unit won't heat or cool that room anymore though. The return air does effect supply air temp. And heat pump efficiency. With a 60 degree return air temp, the heat pump is more efficient then with a 70 degree return air temp.
We are simply getting contaminated causing otherwise healthy folks to lose the function of their kidneys and for a senior citizen who is already suffering sarcopenia this can be a death sentence because of the complexities associated with Renal Failure.
Some muscle mass loss with aging is inevitable, but that doesn't mean you have to end up with sarcopenia, a condition in which loss of muscle mass is associated with a decline in muscle function, according to Roger Fielding, Ph.D., director of the Nutrition, Exercise Physiology and Sarcopenia Laboratory at Tufts University.