How to Use Smart Sensor ST8904 Before Confined Space Entry Malaysia
How to Use Smart Sensor ST8904 Before Confined Space Entry Malaysia
Before entering a manhole, tank, chamber, sewer or other confined space, workers must consider whether the atmosphere contains insufficient oxygen, toxic gases or combustible gas.
The Smart Sensor ST8904 four-in-one gas detector simultaneously monitors:
Oxygen (Oâ‚‚)
Carbon monoxide (CO)
Hydrogen sulphide (Hâ‚‚S)
Combustible gas (LEL)
However, carrying a gas detector is not enough. The detector must be checked, used and interpreted correctly as part of an approved confined-space safety procedure.
Why Test the Atmosphere Before Entry?
A confined space may look safe while containing an invisible atmospheric hazard.
Possible hazards include:
Oxygen deficiency caused by displacement or chemical processes
Oxygen enrichment that increases fire risk
Carbon monoxide from engines or incomplete combustion
Hydrogen sulphide from sewage or decomposing organic material
Flammable vapours or gases that may create an explosion risk
Gas conditions can also change after work begins. Therefore, both pre-entry testing and continuous monitoring may be required.
Step 1: Inspect the ST8904
Before switching on the detector, inspect its general condition.
Check that:
The housing is not damaged
The sensor openings are clean and unobstructed
The display is readable
The battery has sufficient charge
Alarm openings are not blocked
The instrument is within its required inspection or calibration period
Do not use a visibly damaged gas detector without further assessment.
Step 2: Switch It On in Clean Air
Switch on the ST8904 in an area known to have clean, fresh air.
Allow the detector to complete its start-up and warm-up process. Observe the screen and confirm that all four gas channels appear correctly.
The oxygen reading in normal outdoor air should generally be around 20.9% VOL, but actual readings and acceptable limits must be assessed according to the organisation’s procedures and applicable safety requirements.
Do not perform a fresh-air zeroing operation in an area that may already contain gas contamination.
Step 3: Perform a Bump Test
A bump test exposes the sensors to an appropriate known test gas to confirm that the detector responds and its alarms activate.
The test should verify:
Sensor response
Audible alarm
Visual alarm
Vibration alarm
Displayed gas readings
A detector that does not respond correctly during a bump test should not be relied upon for confined-space entry.
A bump test confirms basic response; it does not replace calibration.
Step 4: Confirm the Alarm Settings
The Smart Sensor ST8904 supports several alarm types:
Low alarm
High alarm
STEL alarm
TWA alarm
Alarm limits should follow the company’s safety programme and the applicable occupational exposure requirements. Do not change alarm values simply to prevent frequent alarms.
If the existing settings are unknown, have the instrument checked before use.
Step 5: Test Before Opening or Entering
Where applicable, test the atmosphere from outside the confined space before opening, leaning into or entering it.
Atmospheric conditions can vary according to height:
Some gases may accumulate near the top
Other gases or vapours may collect at the bottom
The middle section may have a different concentration
Testing only one point may not represent the entire confined space.
The standard ST8904 uses diffusion sampling. When the operator cannot safely position the detector at the required testing points, a suitable sampling pump and hose arrangement may be needed.
Confirm the pump compatibility and sampling procedure before use.
Step 6: Allow Time for the Reading to Stabilise
When testing at different levels or locations, allow sufficient time for the air sample to reach the sensors and for the displayed values to stabilise.
The required time can be affected by:
Hose length
Pump flow
Sampling distance
Gas type
Sensor response time
Temperature and humidity
Do not move immediately between sampling points and assume the first displayed value is accurate.
Step 7: Monitor Continuously During Work
Passing a pre-entry test does not guarantee that the atmosphere will remain safe.
Gas concentrations may change because of:
Welding or hot work
Cleaning chemicals
Fuel-powered equipment
Product leakage
Sludge disturbance
Ventilation failure
Work taking place in connected pipelines or chambers
Where required, the worker should wear the detector in the correct breathing-zone position and keep it operating throughout the job.
What Should You Do When the ST8904 Alarms?
Treat every alarm seriously.
The worker should follow the site’s emergency and evacuation procedure, which may include:
Stopping work.
Leaving the confined space immediately.
Warning other personnel.
Reporting the alarm to the entry supervisor or safety officer.
Investigating the cause from a safe location.
Ventilating and retesting before any re-entry.
Never enter or remain in a hazardous atmosphere merely because the displayed reading appears close to the alarm limit.
Can the ST8904 Be Lowered Into a Manhole?
Lowering a diffusion detector may sometimes be considered for preliminary testing, but several practical issues must be addressed:
The detector may be damaged by water or impact
The display may not be visible
Alarm sounds may be difficult to hear
Multiple depths must still be checked
Sufficient response time is required
The instrument may not sample the intended point accurately
For frequent remote or pre-entry sampling, a pumped gas detector with a suitable hose and probe is generally more practical.
Contact MTM Precision before ordering if pump sampling is a requirement.
ST8904 Bump Test vs Calibration
ProcedureMain purposeBump testConfirms sensor response and alarm operationCalibrationCompares and adjusts readings using certified reference gasFunctional inspectionChecks the detector, display, buttons, battery and alarm components
A detector can switch on normally but still fail to respond correctly to gas. That is why functional testing and scheduled calibration are important.
Is the Smart Sensor ST8904 Suitable for Every Confined Space?
No single gas detector is suitable for every application.
The ST8904 monitors the common four-gas combination of Oâ‚‚, CO, Hâ‚‚S and LEL. Another model may be needed when the site requires detection of:
Carbon dioxide
Ammonia
Sulphur dioxide
Chlorine
Volatile organic compounds
Refrigerant gases
Other specialised toxic gases
Customers should identify the expected gas hazards before selecting an instrument.
Get the Smart Sensor ST8904 in Malaysia
MTM Precision supplies the Smart Sensor ST8904 four-in-one gas detector for customers in Malaysia.
Before requesting a quotation, provide us with:
Your work application
Expected gases
Required measuring ranges
Diffusion or pump-sampling requirement
Number of workers or entry teams
Calibration or documentation requirements
Our team can help you determine whether the ST8904 is suitable or whether another multi-gas configuration should be considered.
Contact MTM Precision
MTM Precision Sdn. Bhd.
Office: +603-8080 7172
Desmond: +6019-220 7346
Fifi Ng: +6016-660 7346
WhatsApp: +6019-220 7346
Email: enquiry@mtmpre.com.my
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Serving customers throughout Selangor, Kuala Lumpur, Johor, Penang, Perak, Melaka, Negeri Sembilan, Pahang, Kedah, Perlis, Terengganu, Sabah and Sarawak.
16 Sep 2026
