Introduction

Before you install a Local Exhaust Ventilation (LEV) system, there’s one fundamental principle that determines its effectiveness:

💡 “LEV systems are only as effective as your understanding of the processes and sources of airborne contaminants.” — HSE HSG258, Chapter 4

In other words, if you don’t fully understand how hazardous substances are generated — your LEV system might be targeting the wrong area, capturing too little, or simply failing to protect your workers.

In this article, we’ll break down:

• What are contaminant sources in industrial settings

• Why understanding process emissions matters

• How it shapes LEV system design

• What Malaysian factories can do to stay compliant and safe

What Are “Processes” and “Sources” in LEV Design?

According to HSE’s HSG258 Guidelines (used globally as a best practice, including by DOSH Malaysia):

• A process refers to how airborne contaminants are generated

• A source is where the contaminant is released into the air

For example:

• In woodworking, the process could be sanding or cutting

• The source is the point where dust escapes into the air

• In spray painting, the process is atomisation of liquid

• The source is the tip of the spray gun

✅ Understanding the process = understanding the pattern, timing and intensity of exposure
✅ Understanding the source = knowing exactly where to capture the contaminant

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Types of Contaminant Sources 

1️⃣ Buoyant Sources

• Example: hot fumes from furnaces or soldering

• These rise naturally with temperature

• Needs canopy or rising capture hoods

2️⃣ Injected into Moving Air

• Example: spray guns, atomisers

• High-speed particles move with air current

• Needs close-capture LEV and enclosure

3️⃣ Mechanically Moved

• Example: grinding, sanding, cutting

• Particles are thrown off mechanically

• Capture hoods must be placed close to emission point

4️⃣ Still Air Releases

• Example: slow chemical evaporation

• Diffuses into room air

• Needs enclosures or extracted cabinets

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Why Understanding the Source is Crucial in LEV Projects

✅ Improves Hood Placement
Wrong placement = wasted airflow = poor capture efficiency.

✅ Determines Airflow Volume Needed
Each source type needs different capture velocity (fpm or m/s) and static pressure (in.wg or Pa).

✅ Shapes Duct Sizing & Fan Selection
Overdesign = high energy cost. Undersize = non-compliance.

✅ Ensures Legal Compliance (USECHH 2000 Reg. 17)
DOSH requires your LEV to effectively control airborne exposure — backed by engineering calculations and inspections.

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How ZABSI Designs LEV Systems Based on Real Source Analysis

At ZABSI, we don’t guess airflow. We engineer it.

✅ Step 1: Site Walk & Process Observation
We identify the emission points, task duration, and operator movement.

✅ Step 2: Source Classification
We categorize the source (hot fume, mechanical dust, etc.) and choose the correct capture method.

✅ Step 3: Airflow Calculation
We calculate required capture velocity using HSG258, ACGIH, and DOSH guidelines.

✅ Step 4: Custom LEV Design
Using AutoCAD or CFD modeling, we design the entire duct-fan-filter system to match your process flow.

✅ Step 5: Commissioning & Performance Testing
Smoke tests, airflow meters, static pressure checks — all documented for DOE/DOSH approval.

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Did You Know?

“Many LEV failures are not due to poor equipment, but due to poor understanding of source emissions.”

That’s why cookie-cutter LEV systems don’t work.

If your contractor doesn’t ask how, when and where contaminants are generated — it’s time to reconsider.


📞 Need a Properly Engineered LEV System?

Whether it’s a new process line or an upgrade to an existing LEV, ZABSI ensures your system is:

• ✅ Based on real source analysis

• ✅ Compliant with USECHH Reg. 17

• ✅ Efficient in performance & energy

• ✅ Backed by testing reports and support

📧 Email: sales@zabsi.com
🌐 Visit: www.zabsi.com

LEV design Malaysia, airborne contaminant sources, LEV system engineering, HSG258 Malaysia, DOSH LEV compliance