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.
The Darkest Minds is a relatively new dystopian novel written in December. Unlike other Dystopians cough Gone *Cough!!!* this book does not glorify that children are great and adults are evil, and even though it shows that, it doesn't say it..not really. I really loved this book.