Hot Works Toolbox Talk

Hot work is a fire risk and a cancer risk in the same job

The fire risk is the one everybody already respects. Sparks travel, they drop through gaps, and they sit smouldering in insulation long after the torch has gone down. That is why hot work runs on a permit, and why the fire watch carries on after the work has stopped.

The fume is the newer half. In 2019 HSE changed its enforcement expectations after the International Agency for Research on Cancer concluded that welding fume causes lung cancer, and that this includes mild steel fume. HSE is blunt about what that means in practice: there is no known level of safe exposure, and general ventilation does not achieve the necessary control.

What changed in 2019, in plain terms

Before the alert, plenty of sites treated mild steel welding as the low-risk end of the job: open a door, crack a window, get on with it. HSE will no longer accept welding without suitable exposure control. Indoors that means engineering control, normally local exhaust ventilation. Outdoors it means respiratory protection, because being outside is not extraction and the fume still rises into the welder’s breathing zone under the helmet.

What the law requires

Hot work sits under two regimes at once. Welding fume is a substance hazardous to health, so the Control of Substances Hazardous to Health Regulations 2002 apply in full. The fire and explosion side falls under CDM 2015 and, where flammable gases are in use, DSEAR.

• Assess, then control at source. Assess before the work starts, then prevent exposure or control it adequately at source. Because welding fume causes cancer, exposure must be reduced as low as reasonably practicable. COSHH 2002, regs. 6 and 7.
• Maintain the controls and prove it. LEV must be thoroughly examined and tested at least every 14 months, and tight-fitting RPE must be face fit tested. COSHH 2002, regs. 8 and 9.
• Prevent the fire and explosion risk. Take suitable and sufficient steps to prevent the risk of injury from fire or explosion during construction work. Hot work is controlled by permit. CDM 2015, reg. 29.
• Flammable gases. Where acetylene, LPG or similar are used, assess the risk, eliminate or reduce it, and classify any place where an explosive atmosphere may occur. DSEAR 2002, regs. 5, 6 and 7.

The numbers worth carrying in your head

• APF 20 is the minimum assigned protection factor HSE expects from an arc welder’s RPE, which in practice means powered or supplied air rather than a disposable mask
• 14 months is the longest interval allowed between LEV thorough examinations
• One hour of continuous fire watch after the hot work stops, and a further check two hours after
• Two hours before the site closes is when hot work should finish, so both of those checks can happen

Source: HSE, Change in enforcement expectations for mild steel welding fume (STSU1-2019); COSHH 2002; CDM 2015; HSE, Fire safety in construction (HSG168).

How hot work hurts people

• Welding fume. All of it causes lung cancer, mild steel included, and there is no known safe level. The damage happens on ordinary days when nothing feels wrong.
• Metal fume fever. Flu-like symptoms after a shift, often worst at the start of the working week. It usually passes, and it is also a signal that the controls are not working.
• Sparks and spatter. They travel further than people expect, drop through gaps in the floor and smoulder in insulation for hours before anything shows.
• Acetylene after a flashback. The cylinder can decompose internally and explode. A cylinder that is hot or vibrating is an evacuate and call the fire service job, not a wait and see job.
• Oxygen enrichment. Oxygen leaking or vented into a room soaks into clothing, and flame retardant overalls will then burn fiercely. It is never a way to freshen the air.
• Flashback. The flame travels back into the hose or regulator. Missing or wrongly fitted arrestors are the usual reason it gets that far.
• Hoses. Dragged over sharp edges, run over, burned by spatter, or repaired with tape and a jubilee clip.
• Arc eye and UV. Painful red eyes a few hours after the job, from an arc that was only glanced at, including by people walking past.
• Asphyxiation in confined spaces. Argon, helium and carbon dioxide displace oxygen and collect low down. Tanks, pits and voids are where welders die quickly.
• Noise. Air arc gouging runs at 100 to 115 dB(A) and manual metal arc at 85 to 95 dB(A), well past the point where hearing protection is a duty.

Controls to brief your crew on

• Ask whether it needs welding at all. Cold joining, bolted connections, or steel ordered cut and drilled. Every job designed out is fume and fire risk that never existed.
• No permit, no hot work. Location, method, times, the precautions before, during and after, who is in control and who closes it out.
• Capture the fume at source. On-torch extraction for MIG, an extracted bench for smaller work, or a movable unit that actually gets moved with the job. Filtered if it discharges indoors.
• RPE that does the job. Powered or supplied air at APF 20 or better for arc welding, face fit tested where it has a tight seal, and worn clean shaven at the seal.
• Outdoors still needs RPE. Being outside is not extraction, and the fume still rises into the breathing zone under the helmet.
• Clear the area and screen it. Combustibles moved or covered within the spark zone, including through gaps in the floor, and screens so passers-by are not arc flashed.
• Flashback arrestors at the regulator on both oxygen and fuel gas, spring-loaded non-return valves at the blowpipe, and arrestors at both ends on long hose runs.
• Check for leaks properly. A proprietary leak detection spray approved for oxygen and fuel systems. Never soapy water, never oil or grease, and never a naked flame. Purge the hoses before lighting.
• Cylinders upright, secured and outside. Chained to a trolley or a wall, valves closed when the equipment is not in use, stored outdoors or well ventilated, and never left in a confined space over a break.
• Fire watch, then check again. Continuous for at least an hour after the work stops, a further check two hours after, and hot work finished two hours before the site closes.
• Inspect the kit weekly in demolition and heavy engineering conditions. Replace a leaking hose rather than repairing it, and use crimped clips made for the hose tail.

Source: HSE, Controlling the risks from welding; HSE, Safety in gas welding, cutting and similar processes (INDG297); COSHH 2002, regs. 7 to 9; HSE, HSG168.

Who is competent to do this work

• Welders need to be competent in the process and in the controls that come with it: how the extraction is positioned, how the RPE is checked, and what to do after a flashback.
• Whoever issues the permit must understand the work, the surroundings and the fire watch, and must be the person who closes it out rather than someone who has gone home.
• LEV thorough examination is done by a competent examiner, typically P601 qualified or equivalent, at least every 14 months.
• Face fit testing is carried out by a competent tester for the exact make, model and size of facepiece the welder will wear.

Paperwork that should be in place

• COSHH assessments for the welding process and the consumables, naming the fume controls actually in use.
• Hot work permits, issued, signed and closed out, with the fire watch recorded against each one.
• LEV thorough examination reports, at intervals not exceeding 14 months, with defects closed out.
• Face fit test records naming the exact make, model and size of facepiece.
• Equipment inspection records for hoses, regulators, arrestors and torches, weekly in aggressive conditions.
• Training and competence records, including who may issue a permit.

Five questions to get the crew talking

1. What are we welding or cutting this week, and what is capturing the fume while we do it?
2. Who holds the permit, and who is doing the fire watch after the torch goes down?
3. When was your mask last fit tested, and are you clean shaven at the seal today?
4. Where do the cylinders go at the end of the shift, and are the valves shut?
5. Has anyone had arc eye or flu-like symptoms after a shift, and did anyone report it?

How to run this toolbox talk

1. Read it first and add your site detail: which processes, which consumables, which extraction unit.
2. Pick the moment. Start of shift, at the workface, ten minutes maximum.
3. Show the kit. Hold up the extraction nozzle, the arrestor and the mask, and check them together.
4. Pair it with the fire safety toolbox talk if the crew have not had that one recently.
5. Record who attended on the free toolbox talk sign-in sheet.
6. Close the actions out, especially anything about extraction that is not working.

Frequently asked questions

Is mild steel welding fume really carcinogenic?

Yes. The International Agency for Research on Cancer concluded that welding fume can cause lung cancer, and possibly kidney cancer, and that this includes mild steel fume. HSE issued a safety alert in February 2019 changing its enforcement expectations accordingly. There is no known level of safe exposure.

Is opening a door or window enough when welding indoors?

No. HSE states that general ventilation does not achieve the necessary control. Indoor welding requires suitable engineering controls, normally local exhaust ventilation capturing the fume at source, and where LEV alone does not adequately control exposure it must be supplemented with adequate and suitable RPE.

Do you need RPE for welding outdoors?

Yes. HSE expects appropriate RPE to be provided for welding outdoors. Being outside is not the same as extraction, and the fume still rises into the welder’s breathing zone under the helmet.

What RPE does a welder need?

For arc welding, HSE points to a powered air or supplied air respirator with an assigned protection factor of at least 20. Anything with a tight-fitting face seal must be face fit tested for that exact make, model and size, and worn clean shaven at the seal.

What should you do after a flashback?

Close the cylinder valves on both the fuel gas and the oxygen if it is safe to do so. If the fire cannot be put out immediately, evacuate and call the fire service. Afterwards, inspect the torch, hoses, regulators and arrestors carefully and replace anything damaged. Pay particular attention to acetylene cylinders: if one becomes hot or starts to vibrate it may be decomposing internally, and everyone should be clear of it.

How often should local exhaust ventilation be tested?

At least once every 14 months under regulation 9 of COSHH, by a competent examiner, with the report kept. Daily and weekly user checks sit on top of that: airflow indicator, hoses, filters and seals.