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.
Between 1 and 1.2 g/kg a day seems to be the target for healthy adults. Those with sarcopenia may need 1.2 to 1.5 g/kg a day. Studies show that 12 percent of men and 24 percent of women over age 70 eat significantly less than 0.8 g/kg a day. These higher recommendations do not translate into a lot of extra protein.