What Is Welding Ventilation?- Types and their Examples

A welding ventilation overview

For welding, brazing, soldering, and torch cutting, the main reason for ventilation is to remove air contaminants from the breathing zone. In each case, a different ventilation solution may be needed to remove air contaminants from the welder’s breathing zone.

Ventilation is used to:

• Remove air contaminants from a worker’s breathing zone and work area;
• Prevent the accumulation of flammable or combustible gas or vapor; and,
• Prevent an oxygen-rich or oxygen-deficient atmosphere.

Monitoring devices shall be used to detect a harmful atmosphere. Where adequate ventilation is not practicable, air-supplied respirators or hose masks that are approved for this service are to be used.

In this case, lookouts must be used on the outside of the confined space, which ensures the safety of all individuals working within. Everything in this section indicates requirements for arc, and gas welding and cutting are based on the safety standards established.

Consult a certified industrial hygienist for assistance in determining the specific requirements for your situation as necessary.

Safety in welding, cutting, and allied processes, ANSI (American National Standards Institute) standard Z49.1 Safety in Welding and Cutting.

When using ventilation as a method of protection for a worker, the ventilation system must be used and maintained in accordance with acceptable practices.

When ventilation alone does not meet adequate safe worker protection for the welder, respirators (personal protective equipment) must also be used. Respirators must be selected based on the hazards present, any pertinent legislation, and/or according to CSA standard Z94.4 Respiratory protection germain to the situation.

Factor keep in mind when selecting ventilation

Ventilation selection depends upon:

• Workspace volume
• Workspace configuration
• Number of welders
• Welding process and current
• Consumables used (mild steel, hard facing, stainless, etc.)
• Allowable levels (tlv, pel, etc.)
• Material welded (including paint or plating)
• Natural airflow

Different Types of Ventilation

Ventilation strategies fall into three general categories:

• Natural Dilution Ventilation (least effective)
• Mechanical Dilution Ventilation
• Local Exhaust Ventilation (most effective)

1. Natural Ventilation

Natural ventilation is the movement of air through a workspace generated by natural forces. Outside, this is typically wind. Inside, this may be air movement from open windows and doors.

As per OSHA standards, natural ventilation is generally considered adequate to control exposure to welding and cutting of mild steels, assuming:

• The room or welding area is not less than 10,000 cubic feet (e.g., 22’ W, 22’ L, and22’ H) for each welder.
• The height of the shop ceiling is not less than 16 feet.
• Cross ventilation is not blocked by partitions, equipment, or other structural obstacle. Note: When welding must be performed in a space complete screened on all sides, the screens are arranged in such a manner not to create a serious restriction in ventilation. The screens should be mounted approximately 2 feet above the floor (or the screen would need to extend to the floor to protect nearby workers from welding glare if the work is being done at a low enough level).
• Welding is not performed in a confined space.

Spaces that do not meet these standards must have mechanical ventilating equipment to exhaust at least 2,000 cfm of air for each welder unless local exhaust hoods or booths, or air-line respirators, are being used.

2. Mechanical Ventilation

Mechanical ventilation is defined as air movement through the work space caused by an electrical device (e.g., portable fan, permanently mounted fan in the ceiling or wall).

The minimum flow rate shall be 2000 cfm per welder, except where local exhaust hoods and booths or airline respirators are provided and used. Mechanically ventilated spaces, as defined in OSHA 29 CFR 1910.252(c), include:

• In a space less than 10,000 cubic feet (about 22′ x 22′ x 22′) per welder.
• In rooms with a ceiling height of less than 16 feet.
• In confined spaces, or where the welding space contains partitions, balconies or other structural barriers, in such a way that a gross cross ventilation is substantially obstructed.

3. Local Exhaust Ventilation

Source extraction or local exhaust ventilation (LEV) is a mechanical device used to capture welding fumes at or near the arc and filter the contaminants from the air.

LEV is the most effective way to remove contaminants from the welder’s breathing zone. LEV devices must be able to maintain a velocity of 100 fpm towards the air intake.

Examples of Local Exhaust Ventilation:

• Downdraft Bench: A downdraft bench features a surface with an open grid. Air is drawn down through the grid into exhaust ducting, capturing contaminants. The air speed must be fast enough to prevent contaminants from building up and rising above the breathing zone. If workpieces are very large, they can block the airflow or cause pockets of high-velocity air (this may matter for shielding gases).
• Moveable Hood: Flexible ducting allows the capture hood to be located as required. Provide an air velocity of at least 100 ft/min (0.5 m/s) across the welding arc. Locate the hood as close to the work as practical. The best distance from the arc is about 1 duct diameter.
• Welding Guns with Fume Extraction: The contaminated air is removed just above the source of generation, and moves through a more rigid hose into the exhaust system. The guns can be very effective on flat and vertical surfaces (corners and flanges too).

Ventilation For Fluorine Compounds

Welding or cutting involving flux, coverings, or other materials in sealed spaces where fluorine compounds shall be done according to 2-4 h ventilation in sealed spaces.

A fluorine compound is a compound in which fluorine is an element of the compound and not as a free gas.

Maximum allowable concentration.

The use of local exhaust ventilation or airline respirators for welding or cutting in locations that are not sealed spaces depends upon the individual situation.

However, experience has shown that it is advantageous to ensure protection especially for fixed-position production welding and for all production welding operations on stainless steel.

However, if air sampling at the welding site indicates that fluorides being liberated are at concentrations below the maximum allowable concentration, then protection is not necessary.

Zinc

Zinc Welding Ventilation in Confined spaces, welding or cutting that involves zinc-bearing filler metals or metals with zinc-bearing coatings shall be performed in accordance with the regulations governing confined space ventilation.

Indoors, welding or cutting involving zinc-bearing metals or filler metals with zinc-bearing coatings shall be performed in accordance with local exhaust ventilation regulations.

Lead

Welding with lead-based metals in confined spaces shall comply with local exhaust ventilation guidelines.

Indoors, welding with lead-based metals shall comply with local exhaust ventilation guidelines.

With local exhaust ventilation or airline respirators, welding or cutting indoors or in a confined space with lead-containing metals or lead-bearing paint shall be done using a local exhaust respirator.

Outdoors, you shall wear respirators approved by the US Bureau of Mines, the National Institute of Occupational Safety and Health, or another government agency.

In all cases, local exhaust ventilation or airline respirators shall be worn as needed by any worker who is helping or standing in the vicinity while cutting or welding is being performed.

Beryllium

Welding or cutting indoors, outdoors, or in confined spaces involving beryllium-bearing material or filler metals involves local exhaust ventilation and airline respirators.

This must take place without exception unless atmospheric tests, under the most adverse circumstances, established that the workers’ exposure is at, or below, the acceptable concentrations of the most recent Threshold Limit Values (TLV) of the American Conference of Governmental Industrial Hygienists or Public Law 91-596, Occupational Safety and Health Act of 1970 limits.

In all cases, off-site personnel and workers in the immediate vicinity of welding and cutting operations shall be protected as necessary.

Cadmium

General. Welding or cutting indoors or in confined spaces involving cadmium-bearing or cadmium-coated base metals will use local exhaust ventilation as ventilation and/or air line respirators.

Outdoors, the above operation will take place using respiratory protective equipment, such as fume respirators, certified by the US Bureau of Mines, National Institute of Occupational Safety and Health, or those accredited by the state or other approved testing agency, if followed by their recommendations.

Confined space. Welding (brazing) using cadmium-bearing filler metals will be performed using ventilation as explained in the above paragraph on local exhaust ventilation, and ventilation in confined spaces, and if this work is to be performed in a confined space.

Mercury

When welding or cutting indoors or in confined spaces involving metals coated with mercury-bearing materials like paint, workers shall use local exhaust welding ventilation or airline respirators.

For such operations outdoors, workers shall use respiratory protective equipment certified by one of the following agencies: National Institute of Occupational Safety and Health, US Bureau of Mines, or another agency of government approved for respirator certification testing.

FAQs