Multifunctional Gas Detector

1. Introduction

Thank you for purchasing the GVDA ST8904 Multi-Gas Monitor. This instrument is a portable and handheld device designed for continuous monitoring of four different gases: Oxygen (O2), Hydrogen Sulfide (H2S), Carbon Monoxide (CO), and Combustible Gas (LEL). When these gases are detected, their concentrations are displayed on the LCD. The unit also features configurable high and low alarms, as well as STEL/TWA alarm functions, with audio, vibration, and visual alerts when alarm conditions are exceeded.

To ensure maximum performance and safe operation, please read this user manual thoroughly before use and keep it for future reference.

For a comprehensive guide, you may also refer to the User Manual (PDF).

2. Safety Precautions and Warnings

Improper operation or use in unsuitable environments can reduce the performance and accuracy of this monitor. Always operate the device in a suitable environment and follow these guidelines:

• Read the instruction manual carefully before using the monitor.
• Keep the gas sensor window and gas filter clean. A blocked or dirty filter can cause inaccurate readings.
• Measuring combustible gas in an oxygen-deficient environment may result in readings lower than the actual value. Conversely, in an oxygen-rich environment, readings may be higher than the actual value.
• If the LEL concentration exceeds its range, the unit must be re-calibrated to ensure accuracy.
• Avoid exposure to water vapor of silicon copper compounds or other miscellaneous substances, as these can affect the LEL gas sensor's normal operation and render readings valueless.
• Sudden changes in atmospheric pressure may cause temporary fluctuations in concentration readings.
• Charging the battery or repairing the unit must be performed in a safe environment.
• Do not charge the unit battery in a confined space.
• Replacement parts or sensors are not recommended unless authorized, as this can lead to serious safety problems and void the warranty. Repairs should only be handled by authorized personnel.
• If gas readings exceed the highest unit and then drop suddenly or become unstable, it indicates that the tested gas is beyond the explosion range, which is a very dangerous situation.
• The operating temperature range for this unit is -10°C to 50°C.
• All parts are proprietary; do not change or replace them with unauthorized components. Ship the unit back to an authorized agent for repair if needed.
• This unit must be used with its built-in lithium battery. Do not replace it with other battery types. Do not disassemble the battery in an explosive environment.
• Recharge the battery before it is fully discharged to prevent shortening its lifespan.
• If the unit will not be used for a long period, fully charge it before storage to prevent deep discharge.
• Do not open the cabinet in a dangerous environment.
• The alarm function does not have a hold feature; it will automatically stop once the gas concentration returns to normal.
• Before each use, verify the unit's accuracy with 25% LEL or 50% LEL with Pentane or Methane Cal. Gas cylinder.
• When the measured value is outside the preset alarm level, take immediate action to protect lives and property, especially in explosive environments.

3. Package Contents

The gift box should contain the following items. If any items are missing or damaged, please contact your supplier.

Figure 3.1: Product packaging and contents.

• 1x Multi-Gas Meter (ST8904)
• 1x Instruction Manual
• 1x USB Cable
• 1x Cloth Bag
• 2x Screws

Figure 3.2: Detailed view of included accessories.

4. Product Overview

The ST8904 Multi-Gas Detector features a robust design with a high-quality sensor for accurate measurements, an optional gas sample pump for specialized applications, and a convenient back clip for portability.

Figure 4.1: Front view of the ST8904 Multi-Gas Detector.

4.1 Key Components

Figure 4.2: Labeled components of the ST8904.

• Alarm Light: Visual indicator for alarms.
• LCD Display Panel: Shows gas concentrations, battery status, and menu options. Features HD backlight for easy reading.
• Up Key (▲): Navigation and adjustment button.
• Down Key (▼): Navigation and adjustment button.
• Alarm Sound: Audible alarm indicator.
• Power On/Off Key (⏻): Turns the device on and off.
• Confirm Key (↵): Confirms selections and settings.
• Gas Pump Contact: Connection point for the optional gas sample pump.
• Gas Sensor Windows: Areas where gas sensors are located.

4.2 Key Features

Figure 4.3: Key features of the ST8904.

• High Accuracy Sensor: High sensitivity sensor with short response time and high measurement accuracy for CO, H2S, O2, and LEL.
• Optional Gas Sample Pump: Can be connected to extract air and measure gas quickly in pipelines or narrow spaces.
• Back Clip Design: For convenient carrying and attachment.
• HD Backlight Display: Large color LCD display for easy reading in various lighting conditions.
• Sound, Light, and Vibrate Alarm: Multiple alarm types to alert users when gas concentrations reach critical levels.
• Rechargeable Battery: Equipped with a 3.7V 1800mAh rechargeable battery (BL-9C).

5. Setup

5.1 Battery Charging

The lithium-ion battery should be fully charged before initial use. To charge:

1. Locate the charging port on the right-hand side of the unit, protected by a rubber flap.
2. Plug the connecting lead wire of the battery charger (USB cable) into the charging port.
3. The battery should fully charge within 6 hours.
4. Once fully charged, the unit can operate for approximately 6 hours (without alarm activation).
5. The battery indicator on the LCD will show full when charging is complete.
6. If only one bar remains on the battery indicator, recharge the unit immediately.
7. A periodic alarm sound may indicate a low battery.

Figure 5.1: Charging the 3.7V 1800mAh rechargeable battery.

6. Operation

6.1 Instrument Operation

• Turn On: Press and hold the Power (⏻) button for over 2 seconds. The unit will turn on with a beep sound and vibration, the LCD will light up, display the software version code, and then begin an 18-second countdown. After the countdown, it enters normal gas monitoring mode.
• Turn Off: Press and hold the Power (⏻) button for over 3 seconds. The unit will power off after 3 beep sounds.
• Auto Power Off Function: In normal gas monitor mode, press the Confirm (↵) button until the LCD displays "APO" and either "ON" or "OFF". Use the Up (▲) or Down (▼) button to select "ON" (auto-off after 10 minutes of inactivity) or "OFF" (no auto-off). Press Confirm (↵) to confirm. If auto-off is enabled, a clock icon will appear on the LCD.

6.2 Monitoring Modes

The device offers several monitoring and display modes:

Figure 6.1: Six available operating modes.

• Gases Monitoring Mode: After turning on, the unit defaults to this mode, displaying real-time concentrations of O2, LEL, CO, and H2S.
• View Peak Value Mode: From normal gas monitoring mode, press the Up (▲) key once. This mode shows the peak concentration values for toxic and combustible gases, and the lowest concentration for O2. Press Confirm (↵) to reset peak values.
• View TWA Mode: Press the Up (▲) key twice from normal gas monitoring mode. This displays the Time Weighted Average (TWA) values for toxic sensors. TWA values reset upon power-down, with an 8-hour time base.
• View STEL Mode: From normal gas monitoring mode, press the Up (▲) key three times. This displays the Short Term Exposure Limit (STEL) values for toxic sensors. STEL values reset upon power-down, with a 15-minute time base.

6.3 Alarm Settings

The device supports four alarm setting modes: Low, High, STEL, and TWA.

Figure 6.2: Four modes of alarm setting.

• Low Alarm Setting: From normal gas monitor mode, press the Down (▼) key for 2 seconds. The display will show "ALM. L" and the current low alarm set points. Use the Confirm (↵) button to select a value to adjust, then use Up (▲) and Down (▼) keys to change the value. Press Confirm (↵) to save and move to the next setting.
• High Alarm Setting: Similar to low alarm setting, but accessed after setting low alarms or by navigating from the low alarm screen. The display will show "ALM. H".
• STEL Alarm Setting: Accessed from the alarm settings menu. The display will show "STEL ALM". Adjust values using Up (▲) and Down (▼) keys and confirm with Confirm (↵).
• TWA Alarm Setting: Accessed from the alarm settings menu. The display will show "TWA ALM". Adjust values using Up (▲) and Down (▼) keys and confirm with Confirm (↵).

Figure 6.3: Sound, Light, and Vibrate Alarm in action.

6.4 Calibration Modes

• Zero Calibration Mode: From the zero setup mode screen, press the Confirm (↵) key. The screen will show all values as "Zero" except Oxygen. Press Confirm (↵) again to set gases to zero. If successful, "P" icons will appear. If "F" icons appear, calibration failed; repeat the process.
• Gas Calibration Mode: After entering the correct security code, press the Confirm (↵) key to enter Cal Gas Calibration mode. Follow on-screen prompts to calibrate each gas (Oxygen, Hydrogen Sulfide, Carbon Monoxide, Combustible Gas) using appropriate calibration gas cylinders. Oxygen calibration should be done in fresh air. For other gases, use a mixed cal. gas cylinder with specific concentrations (e.g., 25umol/mol H2S, 100umol/mol CO, 50% LEL Methane).

6.5 Security Code Setting Mode

At the normal gas monitor mode, you can change the security code. Press the Down (▼) key once to enter the security code setting mode. The factory pre-set code is "123". To change it, press Confirm (↵), use Up (▲) and Down (▼) to adjust digits, and Confirm (↵) to confirm each digit. If you forget the security code, press Down (▼) and Up (▲) simultaneously at the security screen to reset.

7. Maintenance

7.1 Cleaning

• Wipe the outside surface of the unit with a soft, clean cloth.
• Never use solvents or harsh cleaning solutions.
• Ensure rubber buttons are free of dirt.
• Clean the sensor opening with a clean, soft cloth or soft brush.

7.2 Battery Care

• Always recharge the battery before it is fully discharged to prolong its lifespan.
• If the meter will not be used for a long time, fully charge the battery to prevent deep discharge.

8. Troubleshooting

• LEL Over Range: If the meter detects an LEL over range, it will continuously alarm. To cancel, turn the unit off and place it in a clean air environment. Re-calibrate the unit after an over-range event to ensure accuracy.
• Calibration Failure: If the display shows an "F" icon during calibration, it indicates failure. Re-calibrate the unit. Ensure you have sufficient calibration equipment and follow the procedure carefully, as incorrect calibration can lead to inaccurate gas measurements.
• Inaccurate Readings: Ensure the sensor window and gas filter are clean. Avoid environments with silicon copper compounds or sudden atmospheric pressure changes.
• Unit Not Responding: Check battery level and charge if necessary. If the unit is unresponsive, contact authorized service personnel.

9. Specifications

Figure 9.1: Dimensions of the ST8904 Multi-Gas Detector.

10. User Tips

• Always perform a simple test before critical use to ensure all functions, including alarms and flashlights, are working correctly.
• The device is CE certified, indicating compliance with European safety standards.
• Ensure the unit is properly calibrated for the specific gases you intend to monitor to achieve accurate results.

11. Warranty and Support

11.1 Quality Warranty

The GVDA ST8904 gas meter is warranted against defects in material and workmanship for a period of one year from the date of purchase. This warranty includes the sensor, battery pack, and optional gas sample pump. The warranty covers defects for 15 months after shipment. If the product is found to be incompatible with this warranty, the sole remedy is repair or replacement of the product, or a refund of the purchase value, at the discretion of Smart Sensor Holding Co., Ltd.

This warranty is valid under the condition that the customer has carefully checked the product upon receipt, ensured it is free of damage, and has operated, maintained, and repaired it strictly according to the user manual. Any maintenance or repair by unauthorized personnel or use of un-certified components will void this warranty.

11.2 Copyright and Declaration

All content in this manual, including text, graphics, and software, is copyrighted by Smart Sensor Holding Co., Ltd. Unauthorized reproduction, reprinting, or disclosure to third parties is prohibited. The company reserves the right to modify and update the content and design specifications of this manual without prior notice.

As the end-user, you are legally bound by battery regulations to return all used batteries and accumulators to designated collection points; disposal in household garbage is prohibited.

12. Frequently Asked Questions

Q: Does this device have a CE mark?

A: Yes, the GVDA ST8904 Multifunctional Gas Detector is CE certified.

13. Appendices: Gas Hazard Information

13.1 Oxygen (O2) and Carbon Monoxide (CO) Gas Hazards

Figure 13.1: Appendix for Oxygen (O2) and Carbon Monoxide (CO) Gas.

13.2 Hydrogen Sulfide (H2S) and Combustible Gas (LEL) Hazards

Figure 13.2: Appendix for Hydrogen Sulfide (H2S) Gas and Combustible (LEL) Gas.