Why Do Environmental Monitors Show Different Readings in a Factory Malaysia
Why Do Environmental Monitors Show Different Readings in a Factory Malaysia
Two environmental monitors placed inside the same factory may not show exactly the same result. This does not automatically mean that one instrument is defective.
Differences may be caused by sensor technology, installation location, response time, airflow, operating conditions and measurement method.
Before rejecting an instrument, the maintenance or safety team should investigate how the readings were obtained.
The Instruments May Use Different Sensor Technologies
Two instruments may measure the same parameter using different sensors or internal calculation methods.
This can affect:
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Sensitivity
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Response time
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Measurement range
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Resolution
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Recovery time
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Cross-sensitivity
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Stability under changing conditions
For example, two particle monitors may process airborne particles differently. Two general VOC instruments may also respond differently to the same chemical mixture.
The displayed parameter name may be identical, but the measurement method may not be exactly the same.
The Monitors Are Not in the Same Location
Environmental conditions can change significantly over a short distance.
Readings may differ when one monitor is:
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Closer to production machinery
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Near a door or window
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Beside a fresh-air outlet
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Close to an exhaust fan
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Near a chemical container
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Positioned higher or lower
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Installed behind an obstruction
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Located in a worker-occupied area
Place the instruments close together if the purpose is to compare their performance.
Airflow Affects the Reading
Factory air does not remain stationary. Fans, extraction systems, air conditioning, doors and moving equipment can create different airflow patterns.
One monitor may receive polluted air directly while another receives cleaner supply air.
Before comparing readings, check:
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Direction of airflow
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Distance from ventilation outlets
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Nearby extraction systems
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Open doors and windows
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Moving vehicles
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Heat-producing machinery
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Physical barriers
An anemometer can help investigate whether airflow is contributing to the difference.
Response Times May Be Different
One monitor may respond rapidly while another averages measurements over a longer period.
When environmental conditions change suddenly, the faster instrument may show the increase first. The other monitor may take longer to reach a similar value.
Response differences are common when:
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Production starts or stops
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A door opens
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Material is poured
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Cleaning chemicals are used
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A vehicle passes
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An exhaust fan is activated
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Workers move close to the sensors
Allow both instruments sufficient time to stabilise before evaluating the results.
Sampling Intervals May Not Match
A data logger may record one measurement every few minutes, while a real-time monitor may update its display every few seconds.
Even if both instruments are functioning correctly, their displayed or recorded results may represent different moments.
Confirm:
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Display update rate
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Logging interval
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Averaging period
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Start time
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Time-zone and clock settings
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Whether the displayed reading is instantaneous or averaged
Synchronising these settings makes comparisons more meaningful.
Temperature and Humidity Can Influence Sensors
Some environmental sensors are affected by temperature and humidity.
Possible effects include:
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Condensation on the sensor
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Slow stabilisation after moving between rooms
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Changes in particle behaviour
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VOC-sensor variation
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Temporary drift
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Inaccurate readings outside the stated operating range
Allow an instrument to adapt when moving it from an air-conditioned office into a hot or humid production area.
One Instrument May Be Measuring a Different Parameter
Similar-looking measurements are not always interchangeable.
Examples include:
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PM2.5 versus total particle count
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TVOC versus one specific VOC
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CO₂ versus estimated CO₂
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Air temperature versus surface temperature
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Relative humidity versus material moisture
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Gas concentration versus a general air-quality index
Check the parameter name, unit and sensing method before comparing results.
Measurement Units May Be Different
A large difference may simply be caused by different units.
Check whether the instruments display:
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ppm
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ppb
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mg/m³
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µg/m³
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Percentage
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Particle count
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Degrees Celsius or Fahrenheit
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Metres per second or feet per minute
Do not compare the displayed numbers until both results have been converted to the same unit.
Sensor Contamination May Affect the Reading
Dust, oil, moisture or chemicals can collect around a sensor inlet.
Warning signs include:
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Slow response
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Readings that do not return to normal
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Repeated unexplained alarms
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Unstable values
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A constant reading in different environments
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Significant disagreement with other instruments
Inspect the sensor inlet and follow the manufacturer’s cleaning instructions. Do not use compressed air, solvents or tools unless the procedure specifically permits them.
Sensor Age and Storage Conditions Matter
Environmental sensors may change as they age. Long storage periods, unsuitable temperature, high humidity or chemical exposure can also affect performance.
Check:
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Manufacturing or purchase date
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Sensor replacement interval
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Battery condition
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Storage history
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Previous exposure to high concentrations
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Warm-up requirements
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Error or warning indicators
A monitor that has been exposed to extreme conditions may require inspection before further use.
Portable and Fixed Monitors May Serve Different Purposes
A portable monitor is usually designed for walkthrough inspection or troubleshooting. A fixed monitor is selected for continuous observation at one location.
Their readings may differ because of:
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Different sensor types
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Different enclosures
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Different airflow through the sensor
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Different update intervals
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Different mounting heights
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Different alarm logic
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Different averaging methods
Models such as the Temtop P600, M2000 2nd and LKC-1000S+ 2nd may be used for portable environmental assessments depending on the required parameters.
A Fosensor FS11301-based system may be considered for continuous fixed monitoring, subject to the selected sensors, range, outputs and alarm configuration.
How to Conduct a Better Comparison
When comparing two environmental monitors:
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Confirm that both measure the same parameter.
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Set both instruments to the same unit.
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Place them close together.
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Keep them away from direct airflow.
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Allow sufficient warm-up and stabilisation time.
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Synchronise the measurement period.
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Compare trends instead of only one reading.
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Repeat the test under stable conditions.
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Check the battery and sensor condition.
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Record the model, location, time and operating conditions.
For critical measurements, use an appropriate reference method or obtain qualified technical assessment.
Do Not Adjust Readings Without Finding the Cause
If two instruments disagree, avoid immediately changing an offset or adjustment value.
First determine whether the difference is caused by:
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Sensor technology
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Location
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Units
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Sampling interval
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Airflow
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Temperature or humidity
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Sensor contamination
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Instrument condition
An incorrect adjustment may make future measurements less reliable.
When Should the Instrument Be Inspected?
Consider further inspection when:
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The difference remains large under stable side-by-side testing.
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The monitor does not respond when conditions change.
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The reading remains fixed.
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The instrument repeatedly shows an error.
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The sensor has been exposed to excessive concentrations.
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Water or chemicals have entered the instrument.
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Alarm behaviour is inconsistent.
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The results could affect an important safety decision.
Provide the supplier with photographs, displayed readings, location details and the comparison method to support troubleshooting.
Conclusion
Different readings between environmental monitors are often caused by location, airflow, sensor technology, response time or measurement settings rather than an immediate instrument failure.
Compare instruments under controlled conditions, confirm that the parameters and units match, and evaluate measurement trends over time.
Understanding the cause of the difference helps factories avoid unnecessary equipment replacement and improves confidence in their environmental monitoring results.
Meta Description: Learn why environmental monitors show different readings in factories in Malaysia. Check sensor type, location, airflow, units, response time and operating conditions.
Contact MTM Precision
MTM Precision Sdn. Bhd.
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
🌐 Website: www.mtmpre.com.my
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01 Sep 2026
