Shenzhen ZhongNuo Testing Technology Co., Ltd. specializes in the certification, calibration, and metrological services for gas alarms, combustible gas detectors, toxic and harmful gas detectors, and other equipment in various locations. We are licensed to serve nationwide, addressing clients' electrical safety and explosion-proof fire prevention concerns, and contributing to safe production.
Flammable and toxic gas detectors calibration and measurement standards:
GB/T50493-2019 "Design Standard for Detection and Alarm Systems of Combustible Gases and Toxic Gases in Petroleum and Chemical Industries"
GB12358-2006 General Technical Requirements for Environmental Gas Detection and Alarming Instruments in Workplaces
JJG 693-2011 "Regulation for Verification of Combustible Gas Detectors"

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, and a manual self-check function should be set for alarm components.
2. Specify the effective detection distance: The effective detection distance of the non-contact gas alarm instrument shall not be less than 20 m.
3. Alarm Value Setting: 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 Regulations 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 instance, the indication error for flammable 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, and calibration programs and corresponding interfaces should be set up to ensure the accuracy of its measurement results.
6. Explosion-proof Performance: Instruments used in explosive environments should possess explosion-proof performance in compliance with relevant regulations and obtain an explosion-proof certification.
7. Audio-Visual Alarm Device: The audio-visual alarm device of the alarm should meet visibility and sound pressure level requirements under specific conditions to ensure effective alerting of staff in emergencies.
8. Output Control Function: Instruments equipped with output control functionality should be capable of initiating the output control function upon emitting an alarm signal, such as cutting off power or activating the exhaust system, etc.
9. Power Requirements: Specific requirements are outlined for the supply voltage, continuous operating time, etc., for battery-powered and non-battery-powered instruments.
10. Additional Performance Requirements: Including specifications for azimuth, 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 resistance, and functionality.

Calibration Method
Appearance and structure
Inspect visually and by touch according to the requirements of 4.1
Logos and Branding Marks
Conduct the visual inspection in accordance with the requirements of Section 4.2.
Power-on inspection
Inspect visually and by touch according to the 4.3 requirements to check the 5.3.4 alarm function and alarm action values.
Introduce a standard gas substance with a concentration exceeding the alarm set point, causing the instrument to trigger an alarm. Observe whether the instrument's audible and visual alarms are functioning properly and record the readings at the time of the alarm. Repeat the measurement three times, with the arithmetic mean of the three readings being the instrument's alarm trigger value.

Power-on inspection
After power on, the instrument should operate normally with clear and complete display sections. Check the alarm function and alarm trigger values.
Alarm function and alarm action value verification
The instrument's sound and light alarm should function normally. Insulation resistance
Insulation resistance for equipment using AC power should be no less than 20MΩ.
Shenzhen ZhongNuo Testing Technology Co., Ltd. is a third-party institution specializing in electrical safety, electrical explosion-proof, gas alarm, and toxic and harmful gas alarm instrument regular calibration, metrology, and verification services, with qualifications to address fire and explosion prevention issues for clients.