How to Check Exhaust Fan Airflow & Ventilation Performance Malaysia

An exhaust fan can be running, making noise and appearing normal while its actual airflow performance has changed.

For factory, warehouse, workshop and building maintenance teams, simply confirming that the fan is rotating may not be enough.

Using an air flow anemometer such as the Benetech GM8902+ allows technicians to measure air movement at an exhaust opening and compare the result with other fans or previous readings.

This can make exhaust ventilation maintenance more objective.

Why Measure Exhaust Fan Airflow?

An exhaust system is designed to move air away from a particular area.

Over time, airflow may be affected by:

Dust accumulation
Dirty filters
Blocked grilles
Fan deterioration
Duct restrictions
Damper problems
Obstructions
Mechanical problems
Changes to the ventilation system

The fan may still rotate even when overall airflow has changed.

Measurement helps maintenance teams identify these changes.

Where Can Exhaust Airflow Be Checked?

Depending on the ventilation system, airflow may be measured at:

Exhaust grilles
Exhaust fan openings
Ventilation outlets
Duct openings
Wall-mounted exhaust points
Selected extraction points

Always choose a measurement location that is appropriate for the system and the purpose of the inspection.

Step 1: Check the Fan Operating Condition

Before measuring, confirm the operating condition.

Record relevant information such as:

Which fan is running?
What operating speed is being used?
Are dampers in their normal positions?
Are nearby doors or openings affecting airflow?
Is the system operating under normal conditions?

This information matters when comparing measurements later.

Step 2: Position the Anemometer

Place the vane sensor of the Benetech GM8902+ Air Flow Anemometer in the moving air.

Keep the sensor appropriately aligned with the airflow.

Avoid randomly changing the sensor position between measurements if the objective is to compare results over time.

Consistency improves the usefulness of the data.

Step 3: Take Multiple Readings

Air velocity may not be uniform across a large exhaust opening.

For example, the centre may have a stronger reading than the edges.

Instead of relying on one point, take measurements at several positions where appropriate.

A simple pattern might be:

Left → Centre → Right

For larger openings, additional measurement points may be required.

Step 4: Compare Similar Exhaust Fans

One of the easiest ways to use an anemometer for maintenance is comparative testing.

Suppose a factory has four similar exhaust fans.

Under comparable operating conditions:

Fan 1 → Reading recorded

Fan 2 → Reading recorded

Fan 3 → Significantly different

Fan 4 → Reading recorded

The different reading at Fan 3 does not automatically prove that the fan has failed.

However, it identifies a location that deserves further investigation.

Step 5: Compare With Previous Measurements

Historical data can be even more useful than comparing different fans.

Establish baseline measurements when the exhaust system is operating normally.

Then perform periodic checks:

Baseline → Month 1 → Month 3 → Month 6

If airflow gradually decreases, the maintenance team can investigate before the reduction becomes more serious.

Measure Before and After Cleaning

Exhaust systems in industrial environments may accumulate dust and contamination.

Airflow measurements can be taken:

Before Cleaning

↓

Clean / Service / Inspect

↓

After Cleaning

↓

Compare

This provides measurable information about changes in airflow condition following maintenance.

Exhaust Fan Running but Airflow Is Weak?

If an exhaust fan is running but measured airflow is lower than expected, technicians can investigate possible causes such as:

Dirty or Blocked Grille

Dust accumulation can restrict the airflow path.

Filter Restriction

Where filters are installed, contamination may reduce airflow.

Duct Restriction

Objects, contamination or other restrictions can affect the air path.

Damper Position

A partially closed or incorrectly positioned damper may affect airflow.

Fan Condition

Mechanical or electrical issues may affect fan performance.

System Changes

Changes to ducts, openings or surrounding equipment can alter airflow behaviour.

An anemometer helps confirm that an airflow difference exists; it does not automatically determine which cause is responsible.

Air Velocity Is Not the Same as Total Airflow

This distinction is important.

An air velocity measurement at one point does not necessarily equal the total volume of air moved by the exhaust system.

Volumetric airflow depends on factors including the velocity distribution and effective opening area.

For engineering verification, commissioning or professional air balancing, technicians should use the appropriate measurement procedures and equipment.

Factory Exhaust Ventilation

The GM8902+ can be useful for routine checks around:

Production areas
Workshops
Warehouses
Mechanical rooms
Equipment rooms
General factory ventilation

Maintenance teams can establish selected exhaust points and periodically compare their measurements.

This makes airflow another condition-monitoring parameter alongside vibration, temperature and electrical measurements.

Can an Anemometer Tell Whether Fume Extraction Is Safe?

No.

An airflow meter alone should not be used to certify that a hazardous fume or contaminant extraction system is safe or compliant.

Where occupational exposure or local exhaust ventilation performance is safety-critical, appropriate professional assessment, measurement methods and applicable standards may be required.

Likewise, an anemometer does not measure the concentration of gases, vapours, dust or other contaminants.

Use the correct instrument and procedure for the specific safety assessment.

Benetech GM8902+ for Exhaust Airflow Checks

The Benetech GM8902+ Air Flow Anemometer is a portable vane-type instrument that can be used for routine airflow measurements at accessible ventilation and exhaust locations.

Potential users include:

Factory maintenance departments
HVAC contractors
Facility management teams
M&E contractors
Ventilation contractors
Warehouse maintenance teams
Building maintenance technicians

For preventive maintenance, a simple approach is:

Measure → Record → Compare → Investigate

Looking for an Exhaust Fan Airflow Meter in Malaysia?

MTM Precision supplies testing and measuring instruments for factory maintenance, HVAC servicing, ventilation inspection, facility management and industrial applications.

Contact MTM Precision

MTM Precision Sdn Bhd
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia

Website: www.mtmpre.com.my
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com

How to Check Exhaust Fan Airflow & Ventilation Performance Malaysia