I had to deal with this exact issue with gas and a/c installs. You do have to be careful when you do any inside/outside venting. With analysis that was done with my A/C unit I should be fine if I open a window in another part of shop, however the volume for my use is not sigificant, 120 cfm, it isn't going to hurt to do it.

Striperman; excellent point!

Salty; If the volume of your building offset the need for make up air with you using many more CFM in your booth!!
The volume of most shops will offset the CFM's from a small exhaust fan.
That was exactly my point re; MSDS! The buisiness gets them the private guy does not!

AdamR.very good post!

Chances are, if everything in the house is NOT running you'll be OK, just be aware of the potential for problems. Do get a CO detector...they're cheap.
I just read about a case that happened a while ago where a family bought a house with a fire place and gas appliances. They never used the fireplace and all was fine. Parents go away for the weekend, teenage daughter stays home and has a few friends over for a sleep over. They light off the fireplace, fall asleep in front of it, parents find them all dead when they get home. The chimney draft was enough to cause a down draft on the gas appliance vent(s). When the system called for heat, it vented directly into the house. Carbon monoxide poisoning was the cause of death.
On a really tight house, 100 cubic feet per minute exhaust might do it. Better safe than sorry.

I agree, that's why I have a externally feed gas fireplace.

I also had to do venting for my make air unit for my gas dryer, so I am aware of the issue. I also had an energy survey done by Baystate Gas and my house isn't that tight.
My stove fan is vented externally and the vent is stuck open, I never fixed it.

It is amazing tho, people with wood stoves, etc. never have this stuff checked. A CO detector is real cheap.

Adam;
In that particular case the fireplace flue or the gas appliance vents were not built to code!! What a shame.

Sea, if the business sells you the product, they are supposed to have a MSDS and should show it to you upon request. If they dont, search the internet. I will check on who to notify if the business does not have the MSDS.

Here's my booth for "water base only" that I use in the basement. Its a computer monitor box with a filter of batting material doubled up to catch the over spray (I keep stealing this stuff from my wife's quilting supplies).

In the back to draw air is a cheap window exhaust fan that I had lying around. Once the box and batting gets caked up in paint, I toss it to the curb and slap another once together. These boxes are always lying around the office.

Here's a pic of the back.

That is definitely, A WHY DIDN'T I THINK OF THAT!!! SOLUTION
I have tons of those boxes at work!!
Nice Idea!

I have tried the box idea, but find that there is one hell of a lot of overspray outside the box, especially if you are hand holding the plugs for effects such as scales and blending colors. My fan was a weak one, and it didn't pull enough air to catch all the overspray. My entire shop ( office ) area was covered with acrilic dust and when I tried to clean it with simple green, it activated the colors and caused one heck of a mess to clean up.