SMART SENSOR ST8904 Multifunctional Gas Detector User Manual

1. Introduction

Thank you for purchasing our multi-gas monitor. This instruction manual provides the necessary information for how to use it, what needs to be careful, and important notices. To get the maximum performance from this product, please read this user manual in detail before use. Also, please keep it in an easy-to-find place for later reference. Before using this instrument, please perform some simple tests to ensure the function is normal.

This professional 4-in-1 gas detector is designed for detecting Carbon Monoxide (CO), Hydrogen Sulfide (H₂S), Oxygen (O₂), and Combustible Gas (LEL). It continuously monitors the gas concentration in the surrounding environment. Once the gas concentration reaches the alarm level, the device will activate sound, vibration, and flash alarms. This high-precision portable gas tester is compact, lightweight, and easy to carry and operate.

2. Safety Warnings and Precautions

WARNING AND PRECAUTION:

• Not suitable operation and use in a bad environment will reduce the performance and accuracy of this monitor. For safe and effective use, please read the following operation procedure and use it in a suitable environment.
• Please read the instruction manual carefully before using the monitor.
• The gas sensor window and gas filter must be kept clean. If the window is blocked or the gas filter is dirty, it will cause the gas sensor reading to be less than the actual measured concentration.
• Measuring combustible gas in a lack of Oxygen environment may cause the reading value to be less than the actual value.
• Measuring combustible gas in an environment full of Oxygen may cause the reading value to be higher than the actual value.
• Every time if LEL concentration had over range, the unit must be re-calibrated again to guarantee the accuracy of the gas meter.
• The water vapor of Silicon copper compound or other known miscellaneous increased, if it affects the normal operation of the LEL gas sensor, it may cause the reading value to be valueless than the actual value.
• Suddenly changes in atmospheric pressure may cause temporary fluctuation of the concentration reading.
• Charging the battery or repairing the unit must be done in a safety environment.
• Prohibited to charge the unit battery under a well.
• Replacement parts or Sensor is not recommended, as it will cause serious safety problems.
• Repair of the unit must be handled by an authorized person or agent. Non-approved parts replaced in the unit will cause malfunction or wrong measurements. Also, reading the user manual before repair is highly recommended.
• Notice: If the gas reading goes over the highest unit and then suddenly drops down or becomes unstable, it means the tested gas is over the exploded range, which is a very dangerous situation.
• The operation range of this unit is from -10 °C to 50 °C.
• All parts cannot be changed or replaced with unauthorized parts. It is highly recommended to ship it back to an authorized agent for repair. Do not connect the unit to other instruments.
• If you need to use a sample pump, you must buy our sample pump, which is designed to fit this unit.
• This unit must work with the built-in lithium battery. Do not replace it with other lithium batteries. Under an exploded environment, do not disassemble the battery.
• Before the battery fully discharges, please charge it on time, otherwise the battery life will be shortened.
• If the unit is not used for a long period, please fully charge it before storage to prevent the battery from fully discharging and shortening its life.

ATTENTION:

• The alarm of this unit has no hold function. When the concentration of gas is over the setup value, it will alarm to alert the end user. After the concentration returns to normal, it will stop automatically.
• Every time before using this meter, please check the unit's accuracy with 25% LEL or 50% LEL with Pentane or Methane Cal. Gas cylinder.
• This meter is a precise measurement apparatus, suitable for use at temperatures between -10 °C to 50 °C.
• Charging battery, repair & replace the unit parts must be operated in a safety environment.
• Replacing parts or sensors with unauthorized third-party components will damage the accuracy and void the warranty of this unit and cause unexpected safety problems.
• For safety, this unit must be operated or repaired by authorized personnel. Before operation, please read this manual in detail.
• When the measured value is less or higher than the alarm level that you preset (the buzzer alarms), please take care to protect people's lives and property in case of explosion.
• In case of repair, do not replace parts with different part numbers and characteristics. This unit cannot be connected to other products without authorization.
• If you need a sample pump, please connect it to our AS8930 sample gas pump, which is powered by the unit itself.
• Prohibited to use third-party batteries not specified by this manual.
• Prohibited to disassemble the battery in an exploded environment.
• Please recharge the battery before it is fully discharged, otherwise it will shorten the battery life or damage the battery.
• If you do not plan to use the meter for a long time, please fully charge the battery to prevent the battery from too much discharge by itself, which can damage the battery.
• Prohibited to open the cabinet in a dangerous environment.
• Certificate: This product complies with the following standards and regulations.

3. Product Overview

Front view of the SMART SENSOR ST8904 Multifunctional Gas Detector.

Detailed diagram of the ST8904 Gas Detector components, including Alarm Light, LCD Display Panel, Up Key, Down Key, Gas Pump Contact, Alarm Sound, Confirm Key, Power ON/OFF Key, and Gas Sensor Windows.

Key features include Smart Sensor technology, Sound/Vibration/Flash Alarm, Battery Charging Function, More Accurate Measurements, Large Color LCD Display, and Low/High Concentration Alarm Setting.

The ST8904 is suitable for various industrial applications such as gas pipelines, ship transportation, metallurgical industry, tunnel construction, and oil exploitation.

The device continuously monitors H₂S and CO gas concentrations and triggers sound, vibration, and flash alarms when levels exceed set limits.

The device is powered by a built-in 1 * Rechargeable BL-9C Lithium-ion 3.7V 1600mAh Battery.

The ST8904 Gas Detector comes with a USB cable, gas calibration hood, storage bag, and user manual.

4. Specifications

Sensor Specifications

Other Specifications

Back view of the device with belt clip and specification label. The label indicates detection ranges for O₂ (0-30% VOL), H₂S (0-500 PPM), CO (0-999 PPM), and Combustible Gas (0-100% LEL), and battery type (3.7V Lithium-ion).

Optional Parts: ST 8930 Sampling Pump

The ST 8930 Sampling Pump can be used with this series gas monitoring meter. It cannot operate separately and must work with the main unit, getting power from it via two contact pins located on the top side of the front panel. The gas flow is 0.5 SCFH (0.25 LPM), and it can sample gas a maximum of 50 feet using a suitable gas tube.

5. Setup

5.1 Unpacking

The gift box should contain the following items. If you find any items missing or pages missing from the instruction manual, please contact your supplier.

• Multi-Gas meter: 1 pcs
• Instruction manual: 1 pcs
• USB cable: 1 pcs
• Screws: 2 pcs
• Gas Calibration Hood: 1 pcs
• Storage Bag: 1 pcs

5.2 Battery Charging

The lithium-ion battery is suggested to be fully charged before using the unit.

1. To charge the battery, plug the connecting lead wire of the battery charger into the charging port located on the right-hand side of the unit. The port is protected by a rubber flap, so you need to release the flap before charging.
2. The battery should be fully charged within 6 hours.
3. Once fully charged, the unit will operate for 6 hours (without alarm).
4. The shaded area of the battery indicator shows full once the battery is fully charged.
5. If only one bar is left on the battery indicator, the battery needs to be charged at once.
6. When the battery is low, the unit might emit a periodic alarm sound to alert you to charge the unit.

6. Operation Manual

6.1 Instrument Operation (Power ON/OFF)

• Turn on the instrument: Depress and hold the Power ON/OFF key (red button) for over 2 seconds. The unit will turn on with a beep sound and vibration. The LCD will light up all icons and segments, then display the software version code. The unit will then go through an 18-second countdown timer. After the countdown, the unit will enter normal gas monitoring mode.
• Turn off the instrument: Depress and hold the Power ON/OFF key for over 3 seconds. The unit will power off after 3 beep sounds.

6.2 Auto Power Off Function

• At normal gas monitor mode, depress the Confirm key (yellow square button) until the LCD displays "APO" and "ON" or "OFF".
• Press the Up/Down keys (yellow triangles) to select "ON" or "OFF".
  • "ON" means the unit will turn off after 10 minutes if no button is activated during this period.
  • "OFF" means no auto power off function.
• Press the Confirm key to confirm your selection. The unit will return to normal gas monitor mode.
• When the unit is set to auto power off mode, an icon will be shown on the LCD. If set to no auto power off, no icon will be displayed.

6.3 Gases Monitoring Mode

After the unit turns on, it will enter normal gas monitor mode. It will real-time monitor the four gases (O₂, LEL, CO, H₂S) continuously and display the updated values on the LCD.

On the left-hand side corner of the LCD screen, there is a battery icon showing the battery power condition. If the power is reduced, the bars inside the battery icon will decrease. If any of the gas concentrations are lower or higher than the user's preset alarm values (including STEL/TWA alarm setup), the unit will activate the alarm signal.

In alarm mode, the unit will alarm with a low-frequency voice (low concentration alarm) or a high-frequency voice (high concentration alarm), light alert, and vibration alert, all active at the same time. In normal gas monitor mode, the user can change the display by pressing the Up key to cycle through different detection modes.

6.4 View Peak Value Display Mode

At normal gas monitor mode, depress the Up key once to enter "Peak value" display mode. In this mode, the screen will show the peak concentration value of the toxic gases and combustible gas, and the lowest concentration value of O₂. Press the Confirm button once to reset the peak value to normal monitor value.

6.5 View TWA Mode

Pressing the Up key two times will put the unit in the View TWA mode. The TWA screen will show the "TWA" icon and a specific icon along with the TWA (Time Weighted Average) value for the two toxic sensors. TWA values are reset every time the instrument is powered down, and the time base is set for 8 hours. TWA is only available for toxic sensors. If the instrument is not equipped with these sensors, this mode will not show.

6.6 View STEL Mode

At normal gas monitor mode, depressing the Up key three times will put the unit in the View STEL mode. The STEL screen will show a specific icon along with the STEL (Short Term Exposure Limit) value for the two toxic sensors. STEL values for the sensor will be reset every time the instrument is powered down, and the time base for STEL is set for 15 minutes. STEL is only effective with toxic sensors. If the instrument does not have these toxic sensors, this mode will not show.

6.7 Alarm Set Points Configuration

The device allows setting of Low Alarm, High Alarm, TWA Alarm, and STEL Alarm values.

6.7.1 Low Alarm Set Points

At normal gas monitor mode, depress the Up key for 2 seconds to enter the low alarm set points screen. The display will show "ALM. L" icon along with four low alarm set points. If no changes are needed, press the Up arrow key to move to the next screen. If changes are desired, press the Confirm key. The first low alarm value will be flashing. To adjust this value, use the Up and Down arrow keys. Once the desired value is met, press the Confirm key to select the next low alarm value. Continue this process until all four low alarm set points have been set. Once all four points are set, the display will again show the four low alarm set points. Pressing the Confirm key will re-enter the mode to set the low alarm levels again. Pressing the Up arrow key will move you to the High Alarm Set Points screen. Pressing the Confirm key at any time will take you back to the initial Low Alarm screen, and no changes will be saved. Pressing the Confirm key a second time will take you to the normal gas reading screen. The low alarm is a non-latching alarm.

6.7.2 High Alarm Set Points

The display will show "ALM. H" icons along with four high alarm set points. If no changes are needed, press the Up arrow key to move to the next screen. If changes are desired, press the Confirm key. The first high alarm value will be flashing. To adjust this value, use the Up and Down arrow keys. Once the desired value is met, press the Confirm key to select the next high alarm value. Continue this process until all four high alarm set points have been set. Once all four points are set, the display will again show "ALM. H" and four high alarm set points values. Pressing the Confirm key will re-enter the mode to set the high alarm levels again. Pressing the Up arrow key will move you to the High Alarm Set Points screen. Pressing the Confirm key at any time will take you back to the initial High Alarm screen, and no changes will be saved. Pressing the Confirm key a second time will take you to the normal gas reading screen. The high alarm is a non-latching alarm.

6.7.3 TWA Alarm Set Points

This section covers the TWA alarm set points screens. The display will show "TWA ALM" icons along with the two TWA alarm set points. If no changes are needed, press the Up arrow key to move to the next screen. If changes are desired, press the Confirm key. The first TWA alarm value will be flashing. To adjust this value, use the Up and Down arrow keys. Once the desired value is met, press the Confirm key to select the next TWA alarm value. Continue this process until both TWA alarm set points have been set. When both values are set, the display will again show "TWA ALM" icons along with the two "TWA" alarm set points. Pressing the Confirm key will re-enter the mode to set the TWA alarm levels again. Pressing the Up arrow key will move you to the TWA alarm Set Points screen. Pressing the Confirm key at any time will take you back to the initial TWA alarm screen, and no changes will be saved. Pressing the Confirm key a second time will take you to the normal gas reading screen.

6.7.4 STEL Alarm Set Points

This section covers the STEL alarm values. The display will show "STEL ALM" and a specific icon along with the two STEL alarm set points. If no changes are needed, press the Up arrow key to move to the next screen. If changes are desired, press the Confirm key. The first STEL alarm value will be flashing. To adjust this value, use the Up and Down arrow keys. Once the desired value is met, press the Confirm key to select the next STEL alarm value. Continue this process until both STEL alarm set points have been set. When both values are set, the display will show "STEL ALM" icon along with the two STEL alarm points. Pressing the Confirm key will re-enter the mode to set the STEL alarm level again. Press the Confirm key once to return to normal gas reading screen.

6.8 Security Code Setting Mode

At the normal gas monitor mode, users can change the security code by depressing the Up key once. The unit will go to security code setting mode screen, displaying "123" as the factory pre-set security code. If you need to change the security code, press the Confirm button. At this time, the first digit of the security code will flash. Press the Up and Down arrow keys to change to the desired digit. If finished, press the Confirm button to confirm the entry. Then it will move to the second digit, which will keep flashing. Repeat the setup for the second and third digits. Once this setup is completed, the display will show the new security code.

WARM HINTS:

If you forgot the security code, you can press down the Up, Down, and Confirm keys at the same time at the security screen. Then you can go to the security setup mode to set up a new security code.

6.9 Gas Calibration Mode

After entering the correct security code, depress the Confirm key. The unit will go to Gas Calibration mode. The user can calibrate the instrument with a calibration gas bottle.

6.9.1 Zero Point Calibration

At the zero setup mode screen, depress the Confirm key. The screen will show all values as "Zero" except Oxygen. Depress the Confirm key again to set the gases to zero point. If the setup is successful, the screen will show three "P" icons at the related locations. If any "F" icon is shown, it means calibration failed, and you need to press the Up arrow key again to repeat the zero calibration.

6.9.2 Gas Concentration Calibration

Press the Confirm key once to enter Oxygen gas calibration mode. You will see a screen similar to the one shown in the manual. Once the digit on the screen becomes stable, press the Confirm key to perform the calibration. If successful, a "P" icon will show. After finishing, it will automatically jump to another three gas calibration screens.

At this step, place the calibration cup firmly on top of the gas sensor, connect the calibration cup with a silicone tube to the passive flow adjustment valve of the Cal gas cylinder, then adjust the flow valve to supply the gas with a speed of 0.5 litre/minute to the gas sensor. Once you find the value of the three gases stable, then press the Confirm button.

If the calibration is successful, the display will show a "P" icon for these four gases, indicating the unit passed this calibration. If the display shows an "F" icon, it means the unit failed this calibration, and you need to re-calibrate again. If calibration passes, press the Confirm key, and the unit will go back to normal gas monitor mode.

Important Notes for Calibration:

• Oxygen calibration should be done in a normal fresh air environment.
• The other three gas calibrations must be fixed. You must use a mixed calibration gas cylinder with the following concentrations: 25umol/mol (PPM) H₂S, 100umol/mol (PPM) CO, 50% LEL Methane.
• Attention: CSA international rules mandate that the calibration gas must be 50% Methane.
• Attention: If the security code is changed, users must follow the security code setting procedure and cannot directly enter calibration mode.
• WARNING: If you do not have enough calibration equipment, do not enter this calibration mode, otherwise the calibration may be changed and the gas measurements may not be correct.

6.10 LEL Over Range Handling

If the meter detects an LEL gas over range, the unit will enter an over range state and continuously alarm. To cancel this over range alarm, you must turn the unit off and then place it in a clean air environment. After an over range event, the unit must be re-calibrated to ensure accuracy.

7. Maintenance

The following guidelines should be followed to achieve good maintenance for the unit.

7.1 Cleaning

• If necessary, wipe the outside surface of the unit with a soft, clean cloth.
• Never use any solvents or cleaning solutions.
• Make sure the rubber buttons are free of dirt.
• To clean the sensor opening, use a clean, soft cloth or soft brush.

7.2 Battery Care

Refer to section 5.2 for detailed battery charging instructions. Proper battery care is crucial for extending the life of the built-in lithium-ion battery.

8. Troubleshooting

• Inaccurate Readings:
  • Ensure the gas sensor window and gas filter are clean. Blockages or dirt can cause readings to be lower than actual.
  • If measuring combustible gas, ensure the oxygen environment is appropriate. Lack of oxygen can cause low readings, while excess oxygen can cause high readings.
  • Sudden changes in atmospheric pressure can cause temporary fluctuations.
  • If LEL concentration has gone over range, re-calibration is required to ensure accuracy.
  • If water vapor or silicon copper compound affects the LEL sensor, readings may be valueless.
• Alarm Issues:
  • If the unit alarms and then the concentration returns to normal, the alarm will stop automatically (no hold function).
  • If the gas reading goes over the highest unit and then suddenly drops or becomes unstable, it indicates the tested gas is over the exploded range, which is a very dangerous situation.
• Calibration Failure:
  • If calibration shows an "F" icon, repeat the calibration process.
  • Ensure correct calibration gas concentrations are used (25umol/mol H₂S, 100umol/mol CO, 50% LEL Methane).
  • Ensure the security code is correctly entered before calibration if it has been changed.
• Battery Not Holding Charge / Short Life:
  • Charge the battery fully before it completely discharges.
  • Fully charge the battery before long-term storage.

9. User Tips

No specific user tips were available from provided reviews or Q&A content.

10. Warranty and Support

10.1 Quality Warranty

We warranty the AS89 Series gas meter against defects in material and workmanship for a period of one year after purchase. This warranty includes the sensor, battery pack, and gas sample pump (if applicable). We also warranty against defects in material and workmanship within 15 months after shipment. SMART SENSOR Holding Co., Ltd. provides no other explicit or implicit warranties, including for sales promotion or special requirements.

If the product is incompatible with the above warranty, the customer's sole remedy and SMART SENSOR Holding Co., Ltd.'s only obligation is to replace or repair the incompatible product, or refund the purchase value.

SMART SENSOR Holding Co., Ltd. is not responsible for any special, accidental, or resulting damages, including lost time and money, arising from the use of this product, whether based on contract or infringement.

The warranty is based on the following conditions: The customer must carefully check the product upon purchase for any damage, perform suitable calibration according to special requirements, and precisely operate, maintain, and repair the product according to the user manual. The warranty is void if maintenance or repair is performed by unauthorized personnel, or if uncertified components or parts are used, causing quality issues.

Any person operating precision instruments must be familiar with the user manual and fully understand its functions and limitations for correct and safe use.

The user is responsible for ensuring that purchased products meet their intended purpose and suitability. Both buying and selling parties must confirm and agree with SMART SENSOR Holding Co., Ltd.

SMART SENSOR Holding Co., Ltd. assumes no liability or responsibility for any suggestions provided to the user.

10.2 Copyright and Declaration

COPYRIGHT

Our company reserves all copyright for this user manual and related contents. Without signed and approved documentation from "Smart Sensor Holding Co., Ltd.", no part of this manual may be plagiarized, reprinted, or copied in any form, including digitalization or electronic methods.

All contents and information in this manual are confidential and belong to the owner. All related copyrights, business marks, business names, patents, and other intellectual property rights are exclusive to "Smart Sensor Holding Co., Ltd." (except as declared otherwise).

Any information (including data, graphics, instruction documents, software lists, signals, or target program code) without signed and approved documentation from "Smart Sensor Holding Co., Ltd." cannot be directly or indirectly disclosed to third parties.

All information and contents are confirmed for accuracy and trustworthiness.

Our company assumes no liability for the user's use of this product in their own way.

Under any circumstances, our company has no liability for any information included in this manual that caused any charges and cost. No notice will be given for changes to this manual.

DECLARATION

• As the end user, you are legally bound (Battery ordinance) to return all used batteries and accumulators; disposal in household garbage is prohibited. You can hand over your used batteries/accumulators at collection points in your community or wherever batteries/accumulators are sold. Disposal: Follow the valid legal stipulations regarding the disposal of the device at the end of its life cycle.
• Our company reserves the right to modify and update the content of this manual and design specifications without further notice.

10.3 Additional Resources

A detailed user manual in PDF format is available for download: View User Manual (PDF).