The other thing to think about is the health part. If you get a spray both that vents back into the room your in, while the filters help, there is only so much they can do, so one that can be vented will be much better. Yes these can be built by yourself, but if 'worse case' it does explode, the insurance is probably not join going to cover any expensese. The odd are slim, but is it worth the money over the long haul. For those who made their own, and have had no problems, great, but that's not for everyone, I agree with mikemodeler in the long run its worth the price. Regardless of which brand, your lungs will thank you.