I've read that one ventilator requirement for COVID-19 is an output filter that prevents the virus (and other viruses and bacteria) from getting into the room a

I've read that one ventilator requirement for COVID-19 is an output filter that prevents the virus (and other viruses and bacteria) from getting into the room air. Otherwise a ventilator is pumping virus into the room air which increases risk for other patients nearby and medical personnel. I'd imagine that worst case these ventilators might be used in large arena's filled with beds rather than positive pressure ICU rooms. Maybe HEPA filters for air purifiers would work? Or HEPA vacuum bags? Or the big filters trucks use for air intake, I think those were used in some early HEPA air filter devices. Not sure if they are fine enough filtering to stop a virus though.