[Silound]

Louisiana doesn't really have much in the way of regs on that, just that the building must be vented to outside air.

I suspect many B&Ms simply are trying to save money where possible. Filtration systems are NOT cheap, and the monthly upkeep can run into the thousands of dollars for carbon filters and closed filter systems. Just an electrostatic filter service costs about 400 a month here.

It really depends on the size of the shop, how much business it does, and if the business owns the building or rents it. A building owned by a modest to larger shop that does $1M+ a year in sales could probably afford a closed return-air filtration system better than a shop that rents a building and does < $500k sales a year.