Welding Fume Extractors for Confined Spaces

Welding in Confined Spaces

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:

• Storage tanks
• Pipelines
• Silos
• Pits
• Process vessels
• Compartments of ships
• Vats
• Reaction vessels
• Boilers
• Ventilation and exhaust ducts
• Sewers
• Underground utility vaults
• Degreasers
• Manholes

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

Based on these factors, qualified individuals may assign a variety of ventilation controls to the operation. These may include continuous general ventilation, local exhaust ventilation, and personal respirators.

When general ventilation is not effective, a local exhaust ventilation approach may be needed. In the next section, we have listed a few local exhaust ventilation solutions that may be effective for certain applications.

IMPORTANT: Air quality sampling and analysis by a Certified Industrial Hygienist or other certified safety professional is typically needed to determine appropriate ventilation and purging equipment.

Local Exhaust Ventilation

Some of the options below have been used in the field for confined space welding.

IMPORTANT: These solutions will not be suitable for every confined space welding or hot work operation. A variety of factors contribute to the selection of proper ventilation methods. You should consult with your qualified safety professional to determine the most effective and safest method for your unique confined space operation. These units are not intended for highly flammable or explosive applications (e.g. when the Lower Flammability Limit is exceeded for any given chemical).

These fume extractors incorporate flame-retardant, steel-ribbed hoses that can be fed through a small opening to reach the operator while the base unit that houses the fan and filtration system can sit outside of the confined area.

In some cases, qualified safety officials may decide to roll the entire unit into the structure if their unique situation allows it.

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.

Model 300, 400, and 450 units are equipped with HEPA filtration [up to 99.97% efficient on particles 0.3 microns]. Not only do these systems remove fumes from the source of emission, they filter the fumes before releasing the air into the immediate environment. The cleanable filters (with use of basic compressed air) on the Model 500 offer MERV 16 efficiency.

Examples:

Pipe Welding

Pipe maintenance welding is an example of confined space welding where these fume extraction units may be suitable. Qualified safety professionals can recommend either rolling the unit into the pipe and utilizing a short extraction arm [Fig. 1 below], or the base of the unit can remain outside of the pipe while the inlet hood of the extraction arm is placed in close proximity to the welding operation [Fig. 2 below].



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.

For additional information on local exhaust ventilation that may be suitable for your confined space operation, give us a call at 1.800.799.4609, email us at sales@sentryair.com, or fill out this simple online form to receive additional information from a Sentry Air Systems Applications Specialist.

Sources

• 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.