Phoenix Journal · LEV Testing
Metal fume fever is a short, flu-like illness that follows exposure to zinc and other metal oxide fumes - unpleasant, easily mistaken for a bug, and a clear warning that fume control has slipped. Here is how to spot it and how to design it out.
Welding & hot work
If a welder feels rough a few hours after cutting galvanised steel - shivery, achy, with an odd metallic taste - it is rarely a coincidence, and it is rarely a virus.
Metal fume fever is one of the most common acute effects of welding and hot work, yet it is often shrugged off as a passing bug. It matters for two reasons. First, it makes people genuinely unwell. Second, it is a signal: if someone has absorbed enough fume to feel it, the extraction and respiratory protection around them are not doing their job, and the same air may be carrying substances far more dangerous than zinc. Below we cover what to look for, what causes it, and how to design the risk out for good.
The tell-tale sign is timing. Metal fume fever does not strike at the torch - it builds several hours later, often after the shift has ended and the welder is at home. That delay is exactly why it gets blamed on a cold.
Metal fume fever is triggered by inhaling freshly formed metal oxide particles, most commonly zinc oxide (ZnO₂ forms as the fume, though it is written ZnO) given off when galvanised or zinc-coated steel is welded, cut or brazed. Copper, magnesium and brass can produce the same effect. The particles are tiny - fine enough to reach deep into the lungs - and it is the body's inflammatory reaction to them that produces the flu-like response.
The dose is what counts. The HSE sets Workplace Exposure Limits (WELs) in its EH40/2005 guidance, which lists individual limits for the metal oxides and gases found in welding fume rather than a single figure for "welding fume" as a whole. Zinc oxide fume carries its own WEL, and the practical goal is simple: keep airborne fume as far below those limits as is reasonably practicable, because for the carcinogenic fraction of welding fume there is no known safe level at all.
That last point reshaped the whole approach to fume in the UK. In February 2019, following an IARC review, the HSE reclassified all welding fume - including mild steel - as a cause of lung cancer and changed its enforcement expectations accordingly. In plain terms, no welding indoors should now take place without effective engineering controls, and where those controls cannot fully clear the air they must be backed by suitable respiratory protective equipment (RPE). Metal fume fever is the acute, visible face of a problem that also has a long-term, invisible side.
Under the Control of Substances Hazardous to Health (COSHH) Regulations, employers work through a hierarchy. Start by removing the coating or choosing a process that produces less fume where you can. Then bring in engineering controls - most often Local Exhaust Ventilation (LEV) - to capture fume at source before it reaches the breathing zone. Position matters enormously: an extraction hood or on-torch capture that sits close to the arc removes far more fume than general room ventilation ever will. Whether an on-torch, torch-mounted arm or an ambient system suits a given bay is a design decision worth getting right, and our guide to welding fume extraction - torch, arm or ambient walks through the trade-offs.
The same principles scale up. Where heavy hot metal work generates large volumes of fume and heat together, capture and airflow have to be planned as a system rather than bolted on afterwards - the thinking behind how foundries manage heat, fume and metal exposure applies to any busy workshop dealing with galvanised or coated stock.
Good practice for prevention comes down to a few disciplines: brief welders on which materials give off zinc, cadmium and other hazardous fumes; keep them out of the plume by working upwind and using capture at source; supply and fit-test the right RPE for residual fume; and maintain the extraction so it keeps performing. That final discipline is where testing earns its place.
LEV that looked effective on the day it was installed drifts out of tune. Ducts fur up, filters load, fans lose pull and hoods get nudged out of position. COSHH Regulation 9 requires a thorough examination and test of LEV at least every 14 months, and the HSE's HSG258 is the benchmark inspectors measure a system against. A proper test confirms the system is still pulling enough air at the hood to actually capture fume, not just make reassuring noise. It is the difference between assuming a welder is protected and knowing it - and it turns metal fume fever from a recurring complaint into an event that simply stops happening.
Questions
Symptoms usually appear 4 to 12 hours after exposure, which is why they often develop in the evening or overnight rather than at the workbench. This delay is a big reason the illness is mistaken for a cold or flu. Symptoms typically peak within a few hours and then settle on their own within 6 to 24 hours.
A single episode of true metal fume fever is generally self-limiting and clears within a day without lasting harm. However, it is a clear sign that fume control has failed, and the same exposure can carry substances that are far more serious - including cadmium, which can cause severe lung damage, and welding fume that the HSE classes as a cause of lung cancer. Repeated episodes should always be investigated, and breathlessness or symptoms lasting beyond 24 hours need medical advice.
The most common cause is zinc oxide fume from welding, cutting or brazing galvanised or zinc-coated steel. Copper, magnesium and brass can produce the same reaction. Because the fume is generated at the arc or flame, any hot work on coated metal in poorly ventilated conditions puts the welder at risk.
Follow the COSHH hierarchy: remove coatings or choose lower-fume methods where possible, then capture fume at source with Local Exhaust Ventilation positioned close to the arc, and back it up with fit-tested RPE for any residual fume. Keep welders out of the plume and brief them on hazardous materials such as galvanised steel and cadmium-bearing rods. Finally, keep the LEV working by having it thoroughly examined and tested at least every 14 months as COSHH Regulation 9 requires.
Phoenix Duct Clean · by the numbers
Phoenix examines and tests local exhaust ventilation to HSG258 and COSHH - measured, reported and certificated, UK-wide.