This is a basic explanation of what an ERV or an air exchanger is and how it might be used in a woodworking environment. What happens is it takes a portion of the inside air and exhausts it outside. At the same time it takes the outside air and brings it in. But, while doing that it takes the energy (heat or A/C) from the inside air and either warms or cools the incoming outside air, but, without mixing the two. So you are not bringing back in the bad inside air but transferring it’s energy. That’s what makes it so efficient. Most of these units have some filtration as well. Somewhere in the 95% @ 5 microns range. The company I used to use was www.stirling-tech.com. You don’t need a lot of air changes per hour, for a normal home .5 air changes per hour (ach) is recommended. What this provides is bringing in fresh filtered outside air and removing the stale polluted inside air in a high efficient manner. The units from Stirling also remove some of the moisture so you don’t need a special drain lie, it is removed with the bad out going air. Most of these units are to be ducted but Stirling used to make a window unit as well, but I’m not sure if they still do.
The biggest savings is reducing the heat or A/C that would be lost by just putting a fan in the window. These units are about 95% efficient.
Now for the the question of using this in a spray or finishing room? I would recommend that in any type of environment that has flammable gases would get an explosion proof unit. That means the motor and any part that can cause a spark is sealed.
I know this is confusing with inside air and outside air but take it slow and educate yourselves before making any decisions. I am just trying to give you some very basic info. This is a very sophisticated technology that is used and in the proper environment can be very useful. Now, will everyone go out and purchase one? I hope not, because not everyone needs it. Some will say this is over kill, but you are the one that has to decide on what is good for your shop and your lungs.
-- Bob K. East Northport, NY