The respiratory hazards involved with welding can reach a new level of danger when the process takes place in confined spaces.
The lack of natural air movement and generally small entry and exit ways does not provide an adequate escape route for toxic fumes and allows fast accumulation.
These hazardous circumstances can present themselves during several other processes as well. Examples include brazing, painting, cutting, sanding, and degreasing.
|Welding the interior of a festoon house.|
According to the National Institute for Occupational Safety & Health (NIOSH) publication “Criteria for a Recommended Standard: Work in Confined Spaces”, confined spaces can be broken down in “Class A”, “Class B”, and “Class C”; however, the broad definition “refers to a space which by design has limited openings for entry and exit; unfavorable natural ventilation which could contain or produce dangerous air contaminants, and which is not intended for continuous employee occupancy […].”
NIOSH lists the following confined space examples:
Compartments of ships
Ventilation and exhaust ducts
Underground utility vaults
The Occupational Safety & Health Administration (OSHA) uses the term “permit-required confined space” to define certain types of confined spaces that may require additional safety controls. You can find the full definition here.
Ventilation & Purging
Ventilation and purging (purging is “the method by which gases, vapors, or other airborne impurities are displaced from a confined space”) are key components in work practices while working in confined spaces and especially when performing hot work in these environments.
Per NIOSH, the method of ventilation necessary is determined by several factors, including:
- Design of the confined space
- Suspected contaminants
- Hazards that arise due to the product stored or produced
- The work to be performed
Some of the options below have been used in the field for confined space welding.
There are two standard arm lengths for these models: 12′ and 25′. Diameters vary from 4″ to 6″ and the magnetic inlet hood can affix to metal materials for hands-free operation.
|Fig. 1: The fume extractor is rolled into the pipe for welding|
|Fig. 2: The base unit of the fume extractor is left outside of the pipe, while the flexible and
flame-retardant hose is taken inside of the pipe and affixed to the metal surface by the magnetic hood.
Festoon House Welding
During the construction of this festoon house, welders utilized the Model 450 fume extractor with 12′ flexible hose. In this case, they chose to keep the base unit in the immediate area, but with the use of a 25′ hose, the unit could be situated outside of the festoon house.
- NIOSH: “Criteria for a Recommended Standard: Working in Confined Spaces”: http://www.cdc.gov/niosh/docs/80-106/80-106.pdf]
- OSHA: “Confined Spaces”: http://www.osha.gov/SLTC/confinedspaces/index.html
- NIOSH: “A Guide to Safety in Confined Spaces” http://www.cdc.gov/niosh/pdfs/87-113.pdf
Disclaimer: This blog entry has been compiled in good faith by Sentry Air Systems, Inc; and no representation is made as to the completeness or accuracy of the information it contains. In particular, you should be aware that this information may be incomplete, may contain errors or may have become out of date. It is the individuals responsibility to verify all information and ensure that the system they utilize is safe for their particular application. Because of the serious nature of confined space welding, consultation by a Certified Industrial Hygienist or other Safety Professional is highly recommended.