Shenzhen ZhongNuo Testing Technology Co., Ltd. is based in South China, specializing in explosion-proof certification and coal mine safety certification application consulting services, offering one-stop explosion-proof technology consulting services.
Explosion-proof certification is the process of verifying that equipment meets the requirements of explosion-proof standards, type testing, and routine tests, and issuing relevant certificates of compliance.
Certificates are available for Ex equipment or Ex components.
The explosion-proof standard GB/T3836 specifies that electrical equipment manufactured in accordance with the explosion-proof type standards listed in GB/T3836 shall be tested.
All must be tested for explosion-proof compliance by authorized national institutions in accordance with the relevant standards and obtain an explosion-proof certificate.
This means that explosion-proof products must obtain the relevant explosion-proof certification.

North American Explosion Proof Certification
The North American explosion-proof certification system (hereinafter referred to as NEC system [NEC: National Electrical Code]) differs significantly from our country's explosion-proof certification system under the support of the national standards (hereinafter referred to as GB system) in aspects such as the classification and grouping of explosive materials, the division of hazardous areas, explosion-proof protection methods, and installation wiring. Currently, North American explosion-proof certification is divided into two major systems: Division and Zone. The Division system uses the explosion-proof marking of the United States, while the Zone system adopts explosion-proof standards consistent with the IEC system.

Limitation requirements for surface resistance of non-metallic casings of explosion-proof equipment
In hazardous areas with explosive dust or gases/vapors, such as coal dust, flour, etc., static electricity may cause fires or explosions, posing significant dangers. Therefore, it is advisable to minimize the use of insulating materials in explosive hazardous areas. When selecting electrical insulating materials, consider maintaining a low insulation resistance to prevent discharge when non-metallic components come into contact with charged parts. For non-metallic insulating materials, the anti-static capability of the equipment can be assessed by measuring the surface resistance of the equipment housing.
Surface Resistance, measured in ohms (Ω), refers to the resistance between two electrical contacts on the measuring surface.
In accordance with the requirements of the IEC 60079 series standards:
1. In Class II explosive gas environments, when the surface area of the non-metallic housing of electrical equipment exceeds a certain limit value (as shown in Table 1), a surface resistance test must be conducted on the non-metallic material to ensure that: by selecting the material, the surface resistance meets at least one of the following requirements when measured according to IEC 60079-0 26.13:
At ≤1 GΩ, (505)% relative humidity;
At ≤100 GΩ, (305)% relative humidity.
2. In environments with Class III explosive dust, if the surface area of the non-metallic housing of electrical equipment does not exceed 500 mm², the risk of static electricity can be disregarded; if it exceeds this limit, a surface resistance test must be conducted for verification. The criteria for assessment are the same as those for the surface resistance test limits in Class II gas environments. For fixed installation equipment that cannot meet the surface resistance limits, an "X" can be added after the "Explosion-proof" symbol, a corresponding warning sign should be placed on the equipment, and the user should be informed in the user manual.

Domestic explosion-proof certification modes are divided into three cases -- Shenzhen Zhongnuo Testing Technology Co., Ltd.
1. Explosion-proof certification system
Applicable Products: Electrical and non-electrical equipment used in places with explosive gases and dust, excluding non-mining applications (except for products listed in the Explosion-proof 3C catalog).
Certification Model: Product Testing
Certification Certificate: Explosion-Proof Compliance Certificate
Certificate Validity: 5 years
Annual Audit Required: No
2. Intrinsically Safe 3C Certification System
Applicable Products: Electrical Equipment listed in the Explosion-Proof 3C Catalog
Certification Model: Combination of Type Testing and Factory Audit
Certification Certificate: CCC Certificate
Certificate Validity: 5 years
Annual Audit Required: Yes, an annual audit is required.
3. Coal Mine Safety/Mineral Mine Safety Certification System.
Applicable Products: Various electrical and non-electrical equipment for use in coal mines and non-coal mines underground
Certification Model: Combination of Type Testing and Factory Audit
Certification Certificate: Mine Products Safety Mark Certificate
Certificate Validity: 5 years
Annual Audit Required: Yes, an annual audit is required
Explosion-Proof Certification Application Consulting Service - Shenzhen Zhongnuo Testing Technology Co., Ltd.