Aluminum is the material of choice for many products, from bicycle frames to aerospace components. But welding aluminum has some specific health hazards that welders should be aware of. Here’s what to know and how welders can protect themselves from inhalation risks when welding aluminum.
What is aluminum used for?
Aluminum (aluminium for our British friends) is one of the most abundant metals found on the planet and second only to iron in its use in metalworking. It is exceptionally lightweight, durable and corrosion-resistant. It is also highly conductive, relatively soft and highly workable compared to many metals. These properties make aluminum and aluminum alloys highly valuable in many different applications across industry, construction and consumer products. Some of the most common uses of aluminum include:
How is aluminum welded?
Aluminum is most frequently welded using either Tungsten Inert Gas (TIG/GTAW) or Metal Inert Gas (MIG/GMAW) methods. Alternative current (AC) TIG welding using a pure tungsten rod and 100% argon as the shielding gas is one of the most popular methods for aluminum welding. MIG welding is also very common for aluminum.
Regardless of the welding method, it is very important to first clean off the oxide layer that forms on the surface of the metal. Aluminum oxidizes readily, forming a hard layer of aluminum oxide at the surface. This layer protects the metal from corrosion, creating one of its most desirable properties. It also has a much higher melting point than the aluminum underneath. For this reason, it must be cleaned off prior to welding. This is typically done using mechanical abrasion.
What are the dangers of aluminum welding fumes?
Aluminum welding produces hazardous fumes, which create significant health risks for the welder. Welding aluminum produces tiny (sub-micron) particles of aluminum, aluminum oxide and other metals found in aluminum alloys, most commonly copper, zinc, magnesium, silicon, manganese and lithium. These small particles can be breathed deeply into the lungs and cross over into the bloodstream, where they can travel throughout the body. Sub-micron aluminum particles can also cross the blood-brain barrier.
Aluminum is a known neurotoxin; while causal links have not been determined, aluminum buildup in the brain has been associated with Alzheimer’s Disease and other neurological problems. Other potential hazards of exposure to aluminum welding fumes include:
- Irritation to the skin, nose, throat, and respiratory passages.
- Metal Fume Fever, a flu-like illness that may result from acute exposure.
- Lung disease, including chronic bronchitis.
- Aluminosis (aluminum dust lung), a type of pulmonary fibrosis (scarring of the lungs) with symptoms of cough and shortness of breath.
Aluminum does not have known carcinogenic or reproductive effects, but other elements found in aluminum alloys or consumables may. Some of the other exposure concerns when welding aluminum include:
- Manganism, a neurological disease associated with exposure to manganese.
- Tungsten exposure from tungsten rods used in TIG welding; tungsten is associated with pulmonary fibrosis; eye, skin, nose and respiratory irritation; nausea; and reproductive effects.
TIG and MIG welding of aluminum also produces ozone. Ozone is classified as a toxic, carcinogenic gas.
What are the exposure limits for aluminum welding fumes?
In the U.S., the Occupational Health and Safety Association (OSHA) sets permissible exposure limits (PELs) for specific substances, including aluminum. The OSHA PEL for aluminum and aluminum oxide are the same: 5 mg/m3 (as respirable dust) and 15 mg/m3 (as total dust) averaged over an 8-hour shift.
The National Institute of Occupational Safety and Health (NIOSH) and the American Council for Governmental Industrial Hygienists (ACGIH) both set occupational exposure guidelines based on the latest scientific evidence. These guidelines do not have the force of law but are considered to be industry best practices and are often used as the basis for future regulation. Both NIOSH and ACGIH have set recommended exposure limits for aluminum lower than the OSHA PEL.
- NIOSH REL: 10 mg/m³ (total dust), 5 mg/m³ (respirable fraction)
- ACGIH TLV: 1 mg/m³ (respirable particulate matter)
Are aluminum welding fumes combustible?
In addition to health hazards, aluminum fumes produced by welding may be combustible. Aluminum dust is highly combustible; it can generate a very strong explosion when suspended in the air in the right concentrations in the presence of an ignition source. Most facilities working with aluminum also conduct cutting, grinding and finishing, creating a highly combustible mix of dust and fumes.
Weld fumes contain a mix of both oxidized and unoxidized metals. While fully oxidized particles are not combustible, the unoxidized portion may be. The combustion risk of aluminum welding fumes depends on the total concentration of fume, the portion that is unoxidized, and other variables. Read more: Are Weld Fumes Combustible?
The combustion risk for a facility depends on the specific characteristics of the dust created by all processes, including welding, cutting, grinding and finishing. To determine whether your specific emissions are combustible, laboratory testing is strongly advised when working with aluminum dust and weld fume. Laboratory testing is conducted to determine the explosive potential of the dust, as measured by the explosion indices (i.e., KST and PMax values). Due to the potentially highly explosive nature of aluminum dust and fumes, it is important to have the specific values to make decisions about dust collector selection and dust collection system design.
What kind of precautions should be taken with aluminum welding fumes?
Welders should not breathe in aluminum welding fumes. Precautions should be taken when welding aluminum, just as with any other form of welding.
- Environmental controls (i.e., source capture or ambient dust collection) must be used to reduce weld fume concentrations in the welder’s breathing zone below the required PEL. Facilities may want to aim for lower NIOSH or ACGIH aluminum exposure limits when designing their weld fume collection strategy.
- When environmental controls cannot keep exposure below the required PEL, PPE should be provided in the form of a NIOSH-approved negative pressure, air-purifying, particulate filter respirator with an N, R or P95 filter.
- Environmental testing may be required to determine occupational exposures and test the efficacy of the dust collection system. This may be in the form of indoor air pollution testing using ambient particulate monitors or exposure testing using devices worn by employees as they go about their normal shift activities.
- If employees have been exposed to aluminum or aluminum oxide fumes above the PEL, medical surveillance may be required, which may include lung X-rays or other tests.
- Dust collection systems must comply with NFPA guidelines for collection of combustible dust to minimize the risk of a dangerous conflagration.
What kind of fume collection system is recommended for aluminum welding?
There are several important considerations when designing a dust collection system for aluminum welding, including:
- What kind of dust collector should be used (e.g., cartridge collector, wet collector, baghouse)?
- What approach should be used for collection: source capture or ambient?
For aluminum welding, a source capture system using a cartridge-style dust collector is usually preferred. Cartridge-style dust collectors come in a range of sizes and filter options and can support high-efficiency filtration for collection of the submicron particles created by welding. They can also be equipped with appropriate fire and explosion safety elements for the collection of explosive aluminum dust. However, in cases where the risk of explosion is very high due to the nature of the dust or other dangers in the facility, wet collection using a scrubber-style dust collector may be recommended. This is why testing the dust to determine its explosive characteristics is so essential.
The source capture solution should be designed to pull welding fumes away from the welder’s breathing zone. For maximum efficiency, collect weld fumes as close to the source as possible.
- Manual welding fumes may be captured using a fume arm or backdraft table or plenum. For MIG welding, a fume gun may also be an alternative.
- Robotic welders should be kept in a hood or enclosure where possible.
Where source capture is not practical or possible, an ambient system may be used to clean air for the whole facility. Ambient air filtration works by circulating air to remove contaminants and introduce fresh, clean air, diluting contaminants below the PEL. Read more: Source Capture vs. Ambient Collection.
What kind of dust collector is recommended for aluminum weld fume?
Regardless of the capture method, it is important to select the right dust collector to filter aluminum weld fumes. A cartridge-style dust collector, such as RoboVent Senturion, is usually recommended for weld fume. These collectors use a pleated filter cartridge to clean contaminants out of the air. A portable fume collector or welding bench with integrated dust collection may be used for individual manual welding stations. There are several considerations in dust collector selection and system design for aluminum weld fumes.
- Filter selection: Because aluminum weld fumes are very tiny (sub-micron), a high-efficiency filter with a MERV 15 rating or higher is recommended (for fabric or cartridge-style dust collectors).
- Dust collector sizing: Dust collector sizing for febric/cartridge collectors comes down to two factors: airflow (CFM) and air-to-cloth ratio (ratio of airflow to filter media area). CFM requirements will depend on the total volume of air that must be moved, the capture velocity that must be maintained for efficient capture, and the static pressure of the system. A systems engineer can determine the best system configuration for a specific application.
- Fire and explosion protection: All dust collectors should be equipped with appropriate fire protection. Collection of combustible aluminum metal dust may require a specialized fire suppression system for suppression of Class D metal dust fires, such as a clean-agent gas or dry chemical system; water sprinklers should not be used when collecting metal dust. If the weld fume is combustible (as determined by a dust hazard analysis), the dust collector must also be equipped with an NFPA-compliant deflagration system.
Need help with aluminum welding fume collection? RoboVent can help you design a system to protect your workers from dangerous aluminum weld fume. Talk to a solution specialist today.