In today's world, facilities face the daunting challenge of minimizing the environmental impact of industrial processes. A primary motivation for industrial plants to control their environmental impact is government regulation. In the U.S., these regulations are issued at the national level by the Environmental Protection Agency (EPA) and similar agencies at the state and local levels.

　　Before the U.S. government passed the first Clean Air Act in 1963, no federal regulations on gaseous emissions existed. The Clean Air Act initiated research to investigate techniques to monitor and control air pollution. During the 1970s and 1980s, the government passed legislation that established a limit on emissions of 10,000 parts per million (ppm) for gases defined as volatile hazardous air pollutants (VHAPs). Similarly in Europe, a series of accidents resulting in toxic chemical release lead to adoption of the European Commission directive 82/501/EEC targeting safety measures to prevent the release of hazardous chemicals.

　　This threshold came down to 1,000 ppm in the 1990s. In some cases, these emissions restrictions were driven even lower by local authorities. The sealing industry has always worked to provide innovative solutions to meet the goals of the regulations and industry.

　　Over time, the seal industry has developed a variety of innovative solutions—single, dual, wet and dry—to continuously reduce fugitive emissions. Emissions control has come a long way, from high-balanced single seals that keep emissions below 500 ppm to dual pressurized liquid seals allowing true zero emissions. Each type of seal—Arrangements 1, 2 and 3—are viable options for low-emissions sealing, but the sealing option selected will depend on the application. When selecting a seal for a zero emissions application, users must define the zero emissions criteria.

　　Acceptable emissions can take on a different definition depending on location and process fluid, as local government defines the acceptable VHAPs emission limit. Sealing solutions may become more elaborate as the total allowable emissions limit trends toward zero, but they are fully able to achieve the goal.