Some of you have asked me where to obtain the filters I used for my varnishing booth. Unfortunately, depending on where you live, they may not be easy to find. In my country, this kind of filters can be bought in large paint and varnish stores. And, of course, they can be bought from varnishing and sanding supplies distributors.
The most important filter is the cardboard one with holes. I've been thinking about it, and I would say that, with some practise, it could be made manually. We would have to use two cardboard sheets with holes, stuck together leaving a small pocket of air between them, and making holes in them that don't line up. If someone wants to give this idea a try, please tell us about your experience!
For the second filter, any kind of filter will do, such as the ones used in dehumidifiers, hoovers and other electrical appliances.
Another thing I've been asked is how often to change the filters:
The first cardboard filter can last forever. The manufacturer says it should be changed when there is too much varnish stuck to it and is too heavy. But even then, it still works! I suppose that if you varnish twice a week, it's good for a year. The dust filter must be cleaned once a month. Especially if you use the booth as air purifier.
After removing it, blow into it. If you see there is too much stuff stuck to it, making it difficult for air to pass, replace it. If, again, you varnish twice a week, you should clean it once a month and replace it every six months more or less.
I'll post a few links I've found on the internet: