Stain-blocking primers are used to cover stains such as watermarks, nicotine (actually tar), markers, smoke, and prevent them bleeding through newly applied layers of paint.
[citation needed] However, in the United States, solvent-based products with high VOC levels still represent approximately 25% of the total market volume for interior stain-blocking primers.
They continue to maintain this significant market share even though many national, regional or local legislations and initiatives concerning the reduction of VOCs have been recently established.
[1] Since their introduction to the US market in 1997, low VOC, odorless stain-blocking primers have become known for their unique combination of highly effective stain blocking technologies.
A good primer has to be compatible with a wide variety of substrates that may be encountered in an interior situation such as: drywall, cement, concrete, plaster and spackling, wood, paneling, old paint, metals, fiberboard, etc.
As state regulatory agencies continue to introduce stricter legislation concerning VOCs, this will pose an even tougher challenge to manufacturers of solvent-based stain-blocking primers.
The values on this chart indicate that the use of mineral spirits based primers would need 6 to 7 air changes per hour requiring significant ventilation.