Why it matters
Hot work is any work that brings heat or an ignition source into an area where flammable materials may be present. Welding, cutting, brazing, soldering, grinding and drilling all count. Sparks travel several metres. They drop through gaps in the floor and can smoulder for an hour before anyone sees smoke.
WSH Council case studies show what goes wrong. A worker died after an oxy-acetylene torch ignited waste oil left in an "empty" drum. In another case, cutting near a silo released flour dust that flashed into a fire and burned two workers. Neither job had a risk assessment or a safe work procedure.
Order of controls
Work down this list from the top. The fire watch is your last line, not your first.
- Avoid hot work. Use cold methods such as unbolting, sawing, pipe cutters or hydraulic shears where you can.
- Move the job. Take the workpiece to a workshop or a designated hot work area away from flammables.
- Remove the fuel. Clear combustibles from the area, clean and purge containers and pipes, and isolate lines that carry flammable material.
- Protect what can't move. Cover it with fire-retardant blankets, metal sheeting or screens, and seal floor and wall openings.
- Control the work. Hot work permit, gas testing, ventilation or fume extraction, trained workers and a fire watch.
- PPE. Welding helmet or face shield with the right filter, flame-resistant clothing, gauntlets, safety boots and respiratory protection where fume cannot be extracted.
The hot work permit
The WSH Council guidelines on flammable materials describe a hot work permit as part of a permit-to-work system. Before work is authorised, a competent person checks that combustibles are removed, gas tests show no flammable atmosphere, and fire protection such as sprinklers, extinguishers and a fire watch is in place.
A good permit names the exact spot, the job, the hazards, the precautions and the PPE. The assessor signs after checking the site. The issuer signs to approve it. The person in charge signs to confirm the crew has been briefed. The permit also needs a handover section for shift changes and a final sign-off after the fire check.
Before signing, the permit issuer should confirm there is no incompatible work nearby, such as spray painting, solvent cleaning or tank draining.
Gas cylinders and equipment
UK HSE guidance on oxy-fuel equipment gives practical rules that apply on any site. Fit flashback arresters on both the oxygen and fuel gas lines near the regulators, and non-return valves at the torch. Purge the hoses before lighting and use a spark lighter.
Check connections for leaks with a proper leak-detection fluid, never a flame. Keep hoses away from sharp edges, traffic and falling spatter. Close the cylinder valves when the job ends or before cylinders are moved. Keep oil and grease away from oxygen fittings, and never use oxygen to blow dust off clothing or to freshen the air.
If an acetylene cylinder becomes hot or starts to vibrate after a flashback or fire, evacuate the area at once and call the fire service. Do not try to move it.
Hot work in confined spaces
Hot work inside a tank, vessel or pit combines two high-risk jobs. It needs a confined space entry permit as well as a hot work permit, and the space must be tested for flammable gas before any torch goes in. Keep gas cylinders and welding sets outside.
The WSH Council Technical Advisory on confined spaces recommends local exhaust ventilation of at least 10 m³/min per welding point. Where that is not practicable, it recommends dilution ventilation of at least 30 m³/min per welder, with blowers outside the space.
What the rules require
In Singapore, hot work falls under the Workplace Safety and Health Act and its regulations. The WSH Council's flammable materials guidelines summarise the duties under the WSH (General Provisions) Regulations:
- Hazardous substances, including flammable materials, are placed under the control of a competent person.
- Reasonably practicable steps are taken to keep sources of heat or ignition apart from flammable materials.
- A means of fire extinguishment is provided, kept readily accessible and tested at regular intervals by a competent person.
- A means of escape in case of fire is provided and kept clear.
- Under the WSH (Risk Management) Regulations, a risk assessment is done before the work and the controls are put in place.
- Hot work inside a confined space also needs a confined space entry permit under the WSH (Confined Spaces) Regulations 2009.
WSH Council guidance points to SS 510, the Singapore Standard Code of Practice for safety in welding and cutting and other operations involving heat. Construction, shipyard and confined space work also carry extra requirements in their own WSH regulations.
The fire watch
The fire watch has one job. They watch for fire. They stand where they can see the sparks land, and they check the far side of walls and the floor below. They hold an extinguisher or have a hose reel ready. They know the alarm point, and they can stop the work.
Keep the watch going after the torch is switched off. HSE notes it is normal to keep the fire watch for 30 minutes after hot work finishes. Many sites keep it longer where combustibles are close. Walk the area once more before you sign off the permit.
Common mistakes
- Calling a drum or tank empty because no liquid can be seen. A small amount of residue is enough to cause an explosion.
- Clearing combustibles from the floor but missing insulation in walls, cable trays or the level below.
- Making the welder their own fire watch.
- Ending the fire watch as soon as the work stops, or at a tea break.
- Running hoses across walkways where vehicles or hot spatter can damage them.
- Leaving cylinder valves open overnight or storing cylinders lying down and unsecured.
- Signing a permit from the office without visiting the site.
Vapour can come from paint, solvent, a drain or the tank next door. Test before you start. Test again after a long break or when anything changes.
Use it on site: the hot work checklist and the toolbox talk to brief your crew.
Sources
- WSH Guidelines on Flammable Materials, WSH Council.
- WSH Guidelines on Managing Safety and Health for SMEs in the Metalworking Industry, WSH Council.
- Technical Advisory on Working Safely in Confined Spaces, WSH Council.
- Risk Management, Ministry of Manpower.
- Workplace Safety and Health (Confined Spaces) Regulations 2009, Singapore Statutes Online.
- Safety in gas welding, cutting and similar processes (INDG297), UK HSE.
This is practical guidance, not legal advice. Laws and codes of practice change; always check the current official text and your site's own procedures.
