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.
Although there is no specific level of lean body mass or muscle mass at which one can say sarcopenia is present (Roubenoff 2001), any loss of muscle mass is of importance because there is a strong relationship between muscle mass and strength (Roth, Ferrell & Hurley 2000).