Shenzhen ZhongNuo Testing Technology Co., Ltd. specializes in the calibration, verification, and metrological services for gas alarms, combustible gas detectors, toxic and harmful gas detectors, and other equipment. We hold qualifications to serve nationwide, providing solutions for various electrical safety and explosion-proof fire prevention issues, contributing to safe production and operation.
Power-on inspection
After powering on the instrument, it should operate normally with clear and complete display. Check the alarm function and the alarm action values.
Alarm function and alarm action value verification
The instrument's acoustic and light alarm should be functioning normally. Insulation resistance.
Insulation resistance for instruments using AC power should be no less than 20MΩ.

Measurement Equipment Control
Instrument control includes calibration, follow-up calibration, and in-service inspection.

Gas Standard Material
The gas standard substances used should be the same type as the gas measured by the instrument, such as methane or other gases, where isopentanol can be used as an alternative. If the instrument does not specify the type of gas being measured, the concentration of the gas with a 60% increase in the alarm set point should be approximately the full scale. The expanded uncertainty of the standard gas generator is not significant (%), and the repeatability of the dilution device should not exceed 1%. The flow rate indication error of the dilution device for concentrated gas standard substances should be no more than 0.%. The concentration unit of the gas standard substances used in the dilution device should be converted to match the indicating unit of the tested instrument, and should not exceed 0.%.

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 the alarm components should also be equipped with a manual self-check option.
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 for different gases according to the standard.
For example, the oxygen deficiency alarm setpoint is 19.5% VOL, and the oxygen-rich alarm setpoint is 23.5% VOL (refer to GB 8958-2006 "Operation Procedures for Oxygen Deficiency Hazardous Work" and GB 30871-2022 "Special Operation Regulations for Hazardous Chemical Enterprises").
The first-level combustible gas alarm setpoint does not exceed 25% LEL, and the second-level alarm setpoint does not exceed 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 Repeatability: 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: Equipment for explosive environments should possess explosion-proof capabilities in compliance with relevant regulations and obtain an explosion-proof certification.
7. Audio-Visual Alarm Device: The alarm's audio-visual alarm device must meet visibility and sound pressure level requirements under specific conditions to ensure 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 outlined for the supply voltage, continuous operating time, etc., for battery-powered and non-battery-powered instruments.
10. Additional Performance Requirements: Includes specifications for bearing, response time, full-range indication error, high-speed airflow, long-term stability, insulation voltage resistance, temperature, constant humidity and heat, electromagnetic interference resistance, steam interference resistance, vibration and drop, and functional aspects.
Shenzhen ZhongNuo Testing Technology Co., Ltd. is a third-party institution specializing in electrical safety, electrical explosion-proofing, gas detectors, and toxic gas alarm instruments for regular inspections, metrological measurements, and calibrations. We are licensed to assist clients in addressing fire and explosion prevention issues.