There are more than 16,000 screen printers in the U.S. and almost 2,000 of them are in California. The vast majority of screen printers are small businesses with fewer than 20 employees. Screen printers use various types of inks to print on a variety of substrates including fabric, paper, metal, glass, wood, ceramics and plastics. Some small screen printers print by hand but most commercial screen printers use automated presses. During printing, some screen printers use cleanup solvents to clean the excess ink from the screens. All screen printers remove the ink from the screens after printing when the screens are saved for the next run or recycled for reuse. The cleaners that are used today may contain toxic materials that pose a risk to workers and community members and virtually all of them are classified as VOCs that contribute to smog. The South Coast Air Quality Management District (SCAQMD) regulates VOC emissions in four counties in southern California. One of the SCAQMD regulations specifies VOC limits for cleanup solvents used in screen printing. The VOC limit is presently set at 750 grams per liter. The regulation was recently modified to reduce the VOC limit to 500 grams per liter on July 1, 2005 and to 100 grams per liter on July 1, 2006.