There are several methods to control hazardous chemicals. The best method is to eliminate it; the next best solution is to substitute a less toxic or less hazardous chemical for the one in use. If the substance in use cannot be engineered out and there is no way to prevent all harmful levels of exposure, then ventilation is used. The next best method is the wear of personal protective equipment and, when there is no way to control exposure, to regulate the amount of time an employee can be exposed to the chemical through administrative controls. A combination of general ventilation (whole area air circulation) and local ventilation is commonly employed.

Local ventilation is provided through vacuum air suction for removing vapors, gases, and particulates at the source of the airborne contamination. It is a major engineering control for removing hazardous chemical vapors, dusts, and fumes from the point of generation. The vacuuming action prevents the contaminant from entering the worker's breathing zone or from entering general air. There are several types and many applications of local ventilation systems.

Use an enclosed hood when conducting chemical experiments and pouring hazardous materials. These types of enclosed hoods are called chemical fume hoods. They control vapor or particle generation during pouring operations, involving highly reactive or corrosive chemicals or carcinogens. These hoods have a lift or swing door for access at the front of the enclosure.

Use the glove box for greater contaminant exposure control. During normal use, the hood can not be opened; operations and manipulations are performed by putting hands and arms into rubberized/flexible gloves. Glove boxes are normally used when the risk of exposure to minute amounts of a hazardous substance can not be tolerated for the amount of time it takes to complete a task.

A commonly used local ventilation vacuum system is the movable "elephant trunk." The exhaust intake is at the end of a movable or fixed position intake system consisting of a hood over the generation point. Examples of local ventilation at the generation point include capture of airborne contaminants generated by use of solvents, cutting oils, soldering and brazing materials.

For more information about the content of this article, consult Material Safety Data Sheets (MSDS)/Globally Harmonized System Safety Data Sheets (SDS), Section 8, "Exposure Control/Personal Protection." For information about references, products, and solutions involving equipment systems to provide local ventilation, click on this link to access the blog, "Using Local Exhaust Ventilation to Control Hazardous Chemical Exposures."