"We’ve Got Ventilation — Isn’t That Enough?"
This is one of the most dangerous assumptions made by site managers, business owners, and even health and safety officers:
“We’ve got windows open and fans running — we’re ventilated.”
Wrong.
There’s a massive difference between general ventilation and Local Exhaust Ventilation (LEV) — and choosing the wrong one could expose your workers to serious, long-term harm.
Let’s break it down.
What Is General Ventilation?
General ventilation is about diluting contaminated air across a large area. Think:
- Windows and doors
- Roof vents
- Ceiling fans
- Mechanical extract or supply systems
It improves comfort, reduces stuffiness, and can slightly reduce airborne contaminants.
But here’s the problem:
It does NOT control dangerous substances at the source.
Why That’s a Major Problem?
Dust, fumes, and vapours behave differently from normal air movement. Many are:
- Heavier than air (e.g. solvent vapours sink)
- Heat-rising (e.g. welding fumes go up)
- Sticky (e.g. oil mist can coat surfaces)
By the time general ventilation dilutes them, your workers have already breathed them in.
What Is Local Exhaust Ventilation (LEV)?
LEV is a targeted, engineered control system designed to:
- Capture airborne contaminants right at the source
- Remove them before they can mix into the workplace air
- Discharge or filter the air safely away from people
It’s the only reliable method to control hazardous airborne substances in high-risk work processes.
Quick Comparison Table
Feature | General Ventilation | Local Exhaust Ventilation (LEV) |
Purpose | Comfort & air dilution | Health protection & contaminant control |
Capture at Source? | ❌ No | ✅ Yes |
Legal Compliance Tool? | ❌ Not sufficient alone | ✅ Required under COSHH Reg. 9 |
Typical Use | Offices, general areas | Dusty, fume-heavy, or hazardous processes |
Health Risk Reduction | 🚫 Minimal | 🛡️ High |
Analogy:
General ventilation is like opening a window while your car exhaust fills the garage.
LEV is like a hose that sucks the exhaust out the moment it’s produced.
Which would you rather have?
Real-World Examples
- Welding in a garage with fans = You’re still breathing metal fumes
- Cutting brick with no LEV = Silica dust hangs in the air for hours
- Spray painting with open doors = Vapour exposure guaranteed
How to Get It Right
- Use LEV systems for all hazardous processes
- Supplement with general ventilation for background airflow only
- Train staff to position hoods correctly
- Maintain and test systems regularly
Bonus Tip: Combine the Two – Smartly
In some environments, the best setup is LEV at source + general ventilation in the background.
But LEV is always your first line of defence when lives are on the line.
Need Help Choosing or Checking Your System?
We design, install, and test LEV systems to meet your specific process needs — and make sure you're legally compliant and operationally safe.
Don’t guess. Know.
→ Book your LEV Audit today.