Shenzhen ZhongNuo Testing Technology Co., Ltd. specializes in the calibration, verification, and metrological services for gas alarms, flammable gas detectors, toxic and harmful gas detectors, and other equipment at various locations. We are licensed to serve nationwide, addressing all kinds of electrical safety and explosion-proof fire prevention issues for clients, and contributing to safe production.
How often should various gas detectors be periodically calibrated and tested?
Instrument recalibration is typically every 1 year, determined by the submitting unit based on actual usage. During the secondary calibration process, if there are doubts about the instrument's test data, or if the main components of the instrument are replaced, as well as after repairs, a recalibration is required.

Gas Standard Material
We use gas standard substances of the same type as the gas measured by the instrument, such as methane, ethane, or other gases. If the instrument does not specify the type of gas being measured, the concentration of the gas at the set point for methane, ethane, or other gases should be approximately 60% of the full scale. The uncertainty of the expanded gas standard substance is not more than % (k-1 standard substance greater than ±1%). The flow indication error of the repetitive dilution device should not be greater than 0.%. The concentration unit of the dilution device for the gas standard substance should be converted to the unit of the instrument being tested when in use. The concentration of the gas standard substance should not be greater than 0.%.

The detection principle of the instruments primarily includes catalytic combustion, infrared absorption, and thermal conductivity types. The sampling methods involve diffusion and aspiration. The instruments are mainly composed of detection elements, amplification circuits, alarm systems, and displays, used for monitoring the concentration of combustible gases in the environment.

Primary Technical Requirements for Regular Calibration of Combustible Gas Detectors (Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
1. Power-On Self-Check Function: The instrument should have an automatic self-check function upon startup, with a manual self-check function for alarm components as well.
2. Specified Effective Detection Distance: The effective detection distance of the non-contact gas alarm instrument shall not be less than 20 m.
3. Alarm Value Settings: Specific alarm value settings are stipulated by the standard for different gases.
For example, the oxygen deficiency alarm setting is 19.5% VOL, and the oxygen-rich alarm setting is 23.5% VOL (refer to GB 8958-2006 "Operation Procedures for Oxygen Deficiency Hazardous Operations" and GB 30871-2022 "Special Operation Specifications for Hazardous Chemical Enterprises").
The first-level flammable gas alarm setpoint is not greater than 25% LEL, and the second-level alarm setpoint is not greater than 50% LEL.
The first and second level alarm settings for toxic and harmful gases are determined based on the OEL (Occupational Exposure Limit) or IDLH (Immediate Danger to Life and Health).
4. Error and Repetition: The standard specifies clear requirements for the instrument's indication error, drift, and repeatability. For example, the indication error for combustible gases, toxic and harmful gases, and oxygen should not exceed 5% FS, 5% FS, and 2% FS respectively within the normal test range of the instrument's full scale.
5. Calibration and Interface: The instrument should be easy to calibrate, with established calibration procedures and corresponding interfaces to ensure the accuracy of its measurement results.
6. Explosion-proof Performance: Instruments used in explosive environments should possess explosion-proof capabilities in compliance with relevant regulations and obtain an explosion-proof certification.
7. Audio-Visual Alarm Devices: The audio-visual alarm devices of the alarm should meet visibility and sound pressure level requirements under specific conditions, ensuring effective alerting of staff during emergencies.
8. Output Control Function: Instruments with output control capabilities should be able to activate the output control function upon emitting an alarm signal, such as cutting off power supply or initiating an exhaust system, etc.
9. Power Requirements: Specific requirements are set for the supply voltage, continuous operating time, etc., of battery-powered and non-battery-powered instruments.
10. Other Performance Requirements: Includes specifications for bearing, response time, full-scale indication error, high-speed airflow, long-term stability, insulation withstand voltage, temperature, constant humidity and heat, electromagnetic interference resistance, steam interference resistance, vibration and drop, and functionality.
Shenzhen Zhongnuo Inspection Technology Co., Ltd. is a third-party institution specializing in electrical safety, electrical explosion prevention, gas alarm systems, and toxic gas detection instruments, offering regular verification, measurement, and calibration services. We hold the necessary qualifications to assist customers in solving fire and explosion prevention issues.