Welding Health and Safety by the Numbers
Chapter 5 of 10 · 10 min read
Respiratory protection
Choose respirators for welding, from disposable masks to powered helmets and supplied air, see how a protection factor divides exposure, why fit matters, and how time without the respirator erodes it.
When extraction and other controls cannot bring a welder’s exposure low enough, or cannot be used at all, the welder wears a respirator. Respiratory protective equipment is the last line of defence in the hierarchy of control, because it protects only the wearer, only while it is worn, and only if it fits and is maintained. Used well, it can reduce a welder’s exposure greatly; used badly, it gives a false sense of security that is worse than none, because the welder and the supervisor believe the exposure is controlled when it is not. The numbers show how much difference the details make.
This chapter describes the kinds of respirator used in welding, explains protection factors and what they mean for exposure, shows why fit, facial hair and the minutes a respirator is lifted matter so much, and covers the selection, fit testing and maintenance that make a respiratory protection programme work. AS/NZS 1715 sets out the selection, use and maintenance of respiratory protective equipment in Australia and New Zealand.
Kinds of respirator
| How it works | Suits | Watch for | |
|---|---|---|---|
| Disposable particulate respirator | tight-fitting filtering half-mask | light, short tasks; under some welding helmets | fit under a helmet; must be fit tested; poor with beards |
| Reusable half-face respirator with particulate filters | tight-fitting mask with replaceable filters | moderate exposures; grinding and cutting | fit testing; filter changes; fits under few helmets |
| Powered air-purifying respirator in a welding helmet | fan blows filtered air into the helmet | most welding where respirators are needed; long shifts | battery and filter care; airflow checks |
| Supplied-air respirator | clean air from a compressor or cylinder through a hose | confined spaces; very high exposures; oxygen-deficient air | air quality; hose management; trained users |
For most welding where respiratory protection is needed, the powered air-purifying respirator built into a welding helmet is the most practical choice. A battery-powered fan on the welder’s belt draws air through a particulate filter and blows it into the helmet, keeping a slight positive pressure that pushes fume away from the face. Because it does not rely on a tight seal against the skin, it works with most facial hair, it is cooler and more comfortable over a long shift, and it fits naturally with the helmet the welder already wears. Tight-fitting masks under welding helmets are often uncomfortable, interfere with the helmet, and are easily disturbed, which matters greatly, as the following sections show.
Protection factors
A respirator’s performance is described by its protection factor: the ratio of the concentration outside the respirator to the concentration inside it. A respirator with a protection factor of 10 reduces the wearer’s exposure to a tenth of what it would be without it. AS/NZS 1715 assigns protection factors to each class of respirator for use in selection, and the respirator chosen must have a factor large enough to bring the exposure inside the facepiece below the exposure standard, with a margin. As an illustration only, a welder exposed to about three times the exposure standard would need a respirator with a protection factor well above three; one with a factor of 10 would bring the exposure inside to about 0.3 times the standard, if it performed as assigned.
That last condition is the important one. Assigned protection factors assume a respirator that fits, is worn correctly, is maintained, and is worn all the time the wearer is exposed. Each of those assumptions can fail.
Minutes without the respirator
A respirator protects only while it is on. Welders lift their helmets to inspect welds, chip slag, change electrodes or talk, and some remove tight-fitting masks because they are hot or uncomfortable. Each minute without protection counts in full, because the fume is breathed unfiltered.
- Protection factor while worn
- 50
- Time not worn
- 10% of the exposed time
- effective factor = 1 ÷ (0.9 ÷ 50 + 0.1) = 1 ÷ (0.018 + 0.1)
- effective factor ≈ 1 ÷ 0.118 ≈ 8.5
- being off for a tenth of the time cuts the protection from 50 to about 8.5
A few minutes off in each hour do more harm than the difference between a good respirator and an excellent one. That is why comfort and convenience are safety features: a powered helmet that the welder can keep on while chipping and inspecting, by flipping up only the filter lens and keeping the head shield and air supply in place, protects far better in practice than a mask with a higher rating that the welder keeps pulling aside.
Fit and fit testing
A tight-fitting respirator works only if it seals against the face; air takes the easiest path, and a gap at the edge of the mask lets unfiltered air in. Faces differ, and a mask that seals on one person may leak on another. Fit testing, done when a tight-fitting respirator is first issued and at intervals after, checks that a particular model and size seals on a particular person, either qualitatively, by testing whether the wearer can taste or smell a test substance, or quantitatively, by measuring the concentration of particles inside and outside the mask. Each wearer also checks the seal every time they put the mask on, by covering the filters and breathing in gently to feel the mask pull against the face.
Facial hair, even a day or two’s stubble, can break the seal of a tight-fitting respirator, and a beard makes a seal impossible. Workers who have beards for personal, cultural or religious reasons need a respirator that does not rely on a face seal, such as a loose-fitting powered helmet or hood. The coordinator’s programme offered powered helmets to every welder who needed respiratory protection, which solved the facial hair question without asking anyone to shave.
Filters
Welding fume is a fine particulate, and the filters must be particulate filters suited to it; the class of filter is chosen with the respirator for the exposure. Gas and vapour filters are needed in addition only where gases such as ozone or vapours from coatings are significant. Particulate filters load up with fume and become harder to breathe through, or, in powered respirators, reduce the airflow; powered units have airflow indicators or alarms, and filters are changed on the maker’s schedule or when the airflow falls. Pre-filters and spark arrestors protect the main filter from spatter.
Supplied air
In confined spaces, where fume concentrations can be very high and the oxygen level may be low, and for the highest exposures in open work, filtering the welder’s air is not enough or not possible, and clean air is supplied from outside through a hose. Supplied-air respirators need breathable air of the right quality, from a compressor with suitable filters and monitoring or from cylinders, hoses that are protected from damage, heat and spatter, and users trained in their use and in what to do if the supply fails. Chapter 8 covers the confined space controls that usually go with them.
Maintenance and storage
Respirators are cleaned, inspected and stored as the maker directs. Powered units’ batteries are charged and checked, their airflow tested before each use, their hoses and seals inspected, and their filters changed. Tight-fitting masks are cleaned after use and stored where they will not be crushed or contaminated. A respirator left on a dusty bench, its filter clogged and its battery flat, is not protection at all, however good it was when it was new, and a welder who picks it up in a hurry may not notice until the fume is already in the helmet. The shop issued each welder their own helmet and respirator, with a storage cabinet at each station and a weekly check by the supervisor.
A respiratory protection programme
Issuing respirators is not enough; the regulator’s guidance and AS/NZS 1715 expect a programme: selection based on the measured exposures and the tasks, fit testing, training in use and limitations, maintenance and storage, supervision to see that respirators are worn, and review using exposure measurements and feedback. A named person, with the time and authority to run it, is responsible for it. The programme’s records, of selection, fit tests, training and maintenance, show that it is real.
Heat, comfort and workload
Respirators add to the burden of hot, heavy work. A tight-fitting mask makes breathing harder and traps heat and moisture against the face; a powered helmet adds weight and a belt-mounted battery and fan. In hot weather, or for heavy work, the extra strain can push a welder towards heat stress, covered in Chapter 9, and makes them more likely to lift the respirator for relief. Powered units, which blow cooling air over the face, are far more comfortable in heat than tight-fitting masks, and some welders who resisted them found that they preferred the helmet to welding without one once summer came. Rest breaks in cool areas, water, and work planned to avoid the hottest part of the day support the respirator programme as well as the welder’s health.
Communication and vision
Welders need to see clearly and talk to their workmates, and respirators can get in the way of both. Masks muffle speech; helmets restrict the view. Modern powered helmets have wide viewing areas, auto-darkening filters that let the welder see the work clearly between welds without lifting the helmet, and some carry communication systems. Choosing equipment that lets the welder see and speak without removing it is part of reducing the time off.
Who needs it and when
The respiratory protection programme states which tasks require respirators, which respirators, and when. The coordinator’s register listed each task’s measured exposure, the controls in place, and whether a respirator was required, recommended or not needed, with the respirator type. Tasks were reviewed after each round of measurements; when extraction brought a task’s exposures well below the standard, the respirator moved from required to recommended, which the welders took as evidence that the measurements, not habit, drove the rules.
The cost of a programme
A powered welding helmet costs much more than a disposable mask, and the programme adds filters, batteries, fit testing, training and supervision. As an illustration, ten powered helmets at about A$2,000 each, with about A$400 a year each in filters, batteries and maintenance, cost about A$20,000 to buy and A$4,000 a year to run, excluding GST. Against that stands the health of ten welders over their working lives, and the cost of the alternative, which in practice is often masks that do not protect. The coordinator presented the cost alongside the exposure measurements, and the owner approved it at the same meeting.
Training the wearer
Every wearer is trained in why the respirator is needed, what it does and does not protect against, how to put it on and check it, how long it may be worn, how to tell when a filter or battery needs changing, how to clean and store it, and what to do if it fails. The training is practical, with the welder’s own equipment, and refreshed each year or when the equipment changes. Welders who understand that a few minutes without the helmet can undo most of its protection keep it on.
The running case: the respirator programme
This is an illustration. The fume survey showed exposures above the standard in the chassis bay before the extraction upgrade, inside box sections even after it, and on galvanised work at some stations. The coordinator issued powered air-purifying welding helmets to the chassis bay welders as an interim measure while the extraction was improved, and permanently to welders on box section and stainless work, with particulate filters chosen with the supplier for the fume. Fit testing was arranged for the few tight-fitting respirators kept for grinding. Within months, the welders’ main complaint was not about wearing the helmets but about the occasional flat battery, which a charging rack at each bay solved.
A failure: the mask under the helmet
This is an illustration. At another shop, welders in a fume-heavy bay were issued disposable masks to wear under their helmets and told to use them. A survey that measured exposures inside the masks found protection far below what the masks were rated for. The welders had lifted their helmets dozens of times an hour, and the masks, pushed aside by the helmets’ headbands, often did not seal at all.
The shop switched to powered helmets and improved its extraction, and the welders’ exposures, measured again, fell well below the standard.
Exercise: protection with time off
A welder’s exposure without a respirator is about 4 times the exposure standard. Their powered helmet performs at a protection factor of about 25 when worn, but the welder lifts it off for about 6% of the exposed time. What is the effective protection factor and the welder’s exposure? If a different habit kept the time off to 1%, what would the exposure be?
With 6% off, the effective factor is 1 ÷ (0.94 ÷ 25 + 0.06) = 1 ÷ (0.0376 + 0.06) ≈ 1 ÷ 0.0976 ≈ 10.2, and the exposure is about 4 ÷ 10.2 ≈ 0.39 times the standard.
With 1% off, the effective factor is 1 ÷ (0.99 ÷ 25 + 0.01) = 1 ÷ (0.0396 + 0.01) ≈ 20, and the exposure about 0.2 times the standard, halving the dose. The habit of keeping the helmet on matters as much as the helmet itself, and better extraction, which lowers the outside concentration, matters most of all.
