On Jun 27, 12:37 am, wrote:
I am an asthma sufferer who is allergic to pollen (big time) and
possibly to dust. I am trying to convert my (small) bedroom into an
"oasis" of clean air to sleep in. So far I've installed a fancy HEPA
filter that recirculates air, I made the windows and the doors air-
tight, and I moved all furniture/stuff out except for the bed. I
checked the air with a laser particle counter, and after 15 min of the
HEPA working at the highest speed the amount of ~1 micron particles in
the air goes down by a facor of 10 compared to the outside air. Great.

The problem is that I don't have any ventilation in the room. And I am
paranoid to leave the windows open. So I am thinking that perhaps the
HEPA recirculating filter I bought was a mistake, and perhaps I
should've installed some sort of a filter that takes the air from the
outside, filters teh air, and blows the air in. What would be the most
affordable way of doing that (under 1k?)? The room is about 12x16
feet, standard height. Wouldn't an outdoor HEPA require replacement
more often than an indoor HEPA? Besides, I rent my house, so, I can't
build/break walls and all that. Minimum impact preferred.

I'm not sure you'll find a through-the-window HEPA filter, but I think
you could jerry-rig one easy enough. Building a small, light frame
that is the same size as a filter and put it in your window and seal
it up. Then put a fan on the inside to suck the air in through the
filter. Then run the inside the room filter, too. Run the window
filter 24/7.

There are many industrial applications of positive pressure of
filtered air including clean rooms and dark rooms. By obtaining
positive pressure, it will blow dust and dirt OUT of the house. When
you open a door, air goes out instead of in -- so the dust and dirt
doesn't come in as easily. You might want to consider putting the
whole house under positive pressure. You don't need much pressure to
be effective -- I'd guess nearly any pressure at all would work. The
trick is to filter the air, force it in, but don't give it an exit so
it (a) pressurizes and (b) goes out through the natural cracks and
stuff where the air would normally be coming in.

Personally, I think you're on the right track. Filtering the air
BEFORE it gets in the room is probably better than filtering it once
it is in the room.

Good luck with it.