Compressed air feels harmless because it's invisible and everywhere. It isn't. Together with fuel, coolant and intake systems under pressure, it causes a steady stream of avoidable workshop injuries, from eye damage to life-threatening ones.
For high-pressure diesel fuel systems specifically, see Working Safely on Turbochargers and Diesel Injectors, which covers fuel injection injuries and depressurising common-rail systems.
1. Compressed air and the body
- Never point compressed air at yourself or anyone else. Air under pressure can enter the body through the skin or body openings and cause serious internal injury, including air entering the bloodstream. It can be fatal.
- Never use compressed air to clean clothing or skin, or to blow dust off yourself.
- "Horseplay" with air lines has killed people. Make it a strict workshop rule.
- Use safety blowguns that limit the outlet pressure and have a guard or diffuser on the nozzle.
2. Eyes and ears
- Wear safety glasses whenever you use a blowgun. Air blows dust, metal swarf and fluids straight back at your face.
- Blow parts clean inside a parts washer or behind a shield, pointing away from yourself and others.
- Wear hearing protection with blowguns and air tools in confined spaces. Sustained exposure damages hearing.
3. Never spin a turbo, or a bearing, with compressed air
It's tempting to "test" a turbo, a cleaned CHRA or a bearing by blowing air through it and watching it spin. Don't.
- Air can spin a turbo shaft far beyond safe speed with no oil supply. The bearings are destroyed in seconds, and in the worst case the wheel can fail.
- The same applies to wheel bearings and any other bearing you've cleaned.
To check a turbo's rotation, turn the shaft by hand only.
4. Air hoses, couplings and hose whip
A hose that comes loose under pressure can whip violently and cause serious injuries.
- Inspect hoses and couplings regularly for cracks, bulges and worn fittings. Replace them, don't repair them.
- Fit whip checks (safety restraint cables) on larger-diameter hose connections.
- Shut off and bleed the air before disconnecting a hose or changing a tool.
- Never kink a hose to stop the air flow while changing a tool.
- Keep hoses off the floor where possible to prevent trip hazards and damage from vehicles.
5. Compressors and air receivers
The air receiver (tank) on a workshop compressor is a pressure vessel, and a failure releases a lot of stored energy.
- Drain condensate (water) from the receiver regularly. Water causes internal corrosion that weakens the tank from the inside.
- Never tamper with or block the safety valve, and test it as recommended.
- Don't exceed the rated working pressure.
- Receivers require periodic inspection and testing under South Africa's Pressure Equipment Regulations (under the Occupational Health and Safety Act). Check your obligations with an approved inspection authority.
- Site the compressor in a ventilated area, away from fuel, solvents and dust.
6. Pressure testing the intake and boost system
Smoke and pressure testing is the fastest way to find boost leaks. Done wrong, it's dangerous.
- Use regulated, low pressure: at or below normal boost pressure. Never connect workshop line pressure directly to an intake system.
- Make sure blanking plugs and adaptors are properly secured. A plug that blows out under pressure becomes a projectile.
- Check that the intake is properly sealed and clamped before pressurising it.
- Stand to the side of joints and plugs while the system is under pressure, not in line with them.
See our Turbo Diagnosis Procedure for the full method.
7. Hot cooling systems
The cooling system runs under pressure at temperatures above boiling point.
- Never open the radiator or expansion tank cap on a hot engine. Coolant can flash into steam and spray out, causing severe scalds.
- Let the engine cool first, then open the cap slowly with a cloth over it, releasing the pressure gradually.
- Use a proper cooling system pressure tester at the specified pressure when checking for leaks.
8. Fuel systems: a quick summary
Fuel systems have two very different pressure zones:
- Low-pressure side (tank, lift pump, filters): low pressure, but fuel leaks and fire are the main risks. Clean up spills, cap open lines, and keep ignition sources away.
- High-pressure side (pump, rail, injector lines): extremely high pressure. Never feel for leaks by hand, wait for the system to depressurise, and replace lines where specified. Full details are in Working Safely on Turbochargers and Diesel Injectors.
9. Truck and commercial tyres
If your workshop handles commercial vehicles:
- Multi-piece and split-rim wheels can separate violently during inflation. Inflate them inside a tyre inflation cage, using a clip-on chuck and a remote gauge so you can stand clear.
- Fully deflate tyres before removing them or working on the rim.
- Never stand in front of the rim during inflation.
10. Make it workshop policy
- Train every staff member on air and pressure safety, including apprentices and casual workers.
- Put the rules where people see them: no compressed air at people, safety glasses with blowguns, no spinning turbos or bearings with air.
- Keep a maintenance and inspection log for compressors, receivers, hoses and pressure testers.
- Make reporting near-misses normal. They're free warnings.
South Africa's Occupational Health and Safety Act requires employers to provide safe equipment, safe procedures and training for their workers.
Tools and parts done properly
Turbo Diesel Components supplies turbochargers, injectors and fitting parts for passenger, commercial and industrial applications. Contact our technical team for fitting and testing advice.