Ventilation of Welding and Cutting Operations

Autoworker develops asthma from exposures below PEL

Welding inside a 16’ diameter steel tube takes place with appropriate Local Exhaust Ventilation. The tube will become a windmill tower. The worker is a member of UAW Local 2297 Beaird Industries. ( Photo by Peter Dooley)

A Michigan autoworker in the body shop of an automobile assembly plant was recently diagnosed as having occupational asthma. MIOSHA investigated the plant as a result of an occupational disease report filed by the worker’s physician. While no exposures were found to be in excess of any permissible exposure limits, the plant was found to be in violation of MIOSHA Rule 3240, which requires local exhaust ventilation when welding zinc-coated (galvanized) metals.

MIOSHA Rule 3240 is similar to OSHA’s requirements for ventilation of welding, cutting, and brazing operations.

Many studies have been conducted on the causes of illness and death of welders. These studies have found an increased risk of serious respiratory diseases, including cancer. The cancer risk cannot be identified with any one specific agent, possibly because of additive effects of the exposure to multiple chemicals. However, the cancer risk does appear to be greater for those welding stainless steels. The bottom line: the International Agency for Research on Cancer has determined that welding fumes are possibly carcinogenic in humans; the National Institute for Occupational Safety and Health (NIOSH) recommends that welding fume exposures be kept as low as possible.

OSHA requirements

Personal Protection Equipment requires regular maintenance. The safety rep above consults with the welder on replacing a worn air hose.

The OSHA ventilation requirements are based on some general observations that welding in either small or entirely screened-in spaces, welding with large numbers of welders, or using materials containing specific metals (such as lead and zinc) or fluoride containing fluxes, will result in excessive exposures. The OSHA rules are summarized below and in the attached table.

Where small spaces are encountered (defined by OSHA as less than 10,000 cubic feet per welder, a ceiling height of less than 16 feet, or impairments to cross ventilation), mechanical ventilation is required. This requirement can be met by using roof or wall fans with a minimum capacity of 2000 cubic feet per minute (cfm) per welder, or by using local exhaust hoods (movable exhaust hoods or fixed enclosures). These hoods must provide a minimum air velocity away from the welder of not less than 100 feet per minute. Where welding and cutting are performed in confined spaces, ventilation must be provided to prevent the accumulation of toxic materials or possible oxygen deficiency. Air exhausted from confined spaces must be replaced with clean air.

Welders equipped with supplied air respirators to protect against harmful fumes.

A number of potentially hazardous materials are employed in fluxes, coatings, coverings, and filler metals used in welding and cutting. Other hazardous materials are released to the atmosphere during welding and cutting. Hazardous materials may include beryllium, cadmium, fluorides, lead, mercury, zinc. Cutting and welding stainless steels release nickle and chromium compounds. Depending on where these materials are used (outdoors, indoors, or confined spaces), the use of local exhaust hoods is required, unless tests can demonstrate that an overexposure will not occur under the most adverse conditions.

Additional help
Specific examples of local exhaust hoods found to be effective in reducing welding exposures can be found in Industrial Ventilation, A Manual of Recommended Practice. This book is published by the American Conference of Governmental Industrial Hygienists (ACGIH). It is available directly for purchase from ACGIH at their website: www.acgih.org.

The OSHA regulations can be found at: www.osha.gov. Additional information on the hazards of welding are available from NIOSH at www.cdc.gov/niosh.

Useful fact sheets on the health and safety aspects of welding are available for download (free of charge) from the American Welding Society at www.aws.org.