Ex ma vs Ex mb vs Ex mc at a glance
IEC 60079-18:2025 is Edition 5.0, published on June 19, 2025. It covers the construction, testing and marking of electrical Ex Equipment, parts of Ex Equipment and Ex Components using encapsulation m for explosive gas atmospheres or explosive dust atmospheres. The publication replaced the 2014 fourth edition and Amendment 1:2017.
| Suffix | Level identified by the suffix | Public voltage-scope ceiling | Safe procurement conclusion |
|---|---|---|---|
| Ex ma | Level of Protection ma |
Rated voltage not exceeding 1 kV AC RMS or DC | Record the complete marking and verify its stated EPL, atmosphere, group, temperature data and certificate evidence |
| Ex mb | Level of Protection mb |
Rated voltage not exceeding 11 kV AC RMS or DC | Do not treat the higher scope ceiling as proof of a higher offered rating, Zone permission or interchangeability |
| Ex mc | Level of Protection mc |
Rated voltage not exceeding 11 kV AC RMS or DC | Confirm the exact EPL and application from the full marking, certificate and controlled instructions |
The table reports only information available in the standard's public scope. A scope ceiling is not a product rating or Zone permission.
What encapsulation m establishes
Encapsulation m is a defined type of protection, not a casual description for a potted electronic part. IEC 60079-18 adds particular requirements to the general Ex equipment framework. It supplements and modifies IEC 60079-0:2026, the current Edition 8.0 general standard published on June 16, 2026. Where Part 18 conflicts with a Part 0 requirement, the Part 18 requirement takes precedence within its scope.
A datasheet statement such as encapsulated, resin filled or weather sealed does not demonstrate compliance with IEC 60079-18. The assessed construction, marking, tests and certificate records must support the offered identity. An IP rating does not establish type of protection m.
This guide intentionally gives no universal encapsulant formulation, thickness, curing condition, void acceptance rule, temperature allowance, repair method or fault-count rule. Those details cannot safely be reconstructed from a suffix. They depend on the controlled standard, assessed construction, certificate documentation and manufacturer instructions.
Gas and dust scope needs a complete marking
IEC 60079-18:2025 addresses equipment intended for explosive gas atmospheres or explosive dust atmospheres. This does not mean every encapsulated item is approved for both. The offered nameplate and certificate must show the actual atmosphere, group, temperature information and EPL that were assessed.
Use the MMAIATEX guide to Equipment Protection Levels for EPL definitions, then return to the exact equipment evidence. Use the separate guide on how to read Ex markings to follow the complete marking chain. Neither guide should be used to fill a missing field by inference.
The Part 18 public scope also says it does not account for a hazard caused by emission of flammable or toxic gas from dust. If a process material can release such gas, the responsible engineering team must assess that separate hazard. A dust marking or an encapsulation suffix does not close that review.
Why the 1 kV and 11 kV limits can be misread
The 1 kV limit for ma and the 11 kV limit for mb and mc define where the document applies. They do not state that a particular item is rated at either value. They also do not prove insulation coordination, circuit duty, temperature performance or suitability for the available supply.
A buyer cannot select mb instead of ma simply because the operating voltage falls below both public ceilings. Any offered rating still requires exact documentary confirmation.
Read suffix, EPL and certificate together
For each offered configuration, capture the full marking exactly as supplied. At minimum, the review should connect these fields:
- Legal manufacturer and exact product or component identity
- Model, suffix, variant and option codes
- Complete gas, dust or other applicable Ex marking
ma,mbormcsuffix and the stated EPL- Equipment group and temperature class or maximum surface-temperature information, as applicable
- Certified ambient range and electrical ratings
- Certificate number, issue, current status, scope and schedule
- Specific conditions, component limitations and controlled instructions
The IECEx recognized standards list identifies IEC 60079-18 as the equipment-protection standard for encapsulation m. It does not certify a product and does not replace the exact certificate in the IECEx online certificate system.
X, U and assembly boundaries
If an IECEx certificate number carries an X suffix, obtain and resolve the Specific Conditions of Use for the exact equipment. If it carries a U suffix, treat the record as an Ex Component certificate and verify the conditions for incorporation into the complete equipment or assembly. The MMAIATEX guide to IECEx certificate X and U suffixes explains this document handoff without replacing the live certificate.
Encapsulated parts can affect interfaces outside the encapsulant. Connections, protective concepts used elsewhere in the assembly, temperature behavior, mechanical protection, enclosure arrangements and installation conditions may remain relevant. A component certificate does not become a certificate for the finished assembly merely because the component is installed without modification.
Procurement evidence checklist
Before approving an Ex ma, Ex mb or Ex mc item, request and cross-check:
- Manufacturer legal name, model, suffix and offered configuration
- Full nameplate artwork or legible marking record
- Current certificate and complete schedule for the exact identity
- Declared gas or dust application, EPL, group and temperature information
- Rated voltage, current, frequency where applicable and certified ambient range
- Every
Xcondition orUintegration limitation - Controlled installation, operation and maintenance instructions
- Drawings and interfaces needed to assess incorporation into the final assembly
- Destination-market declarations and other required conformity documents
- Change-control confirmation for substitutions, options and revisions
The earlier MMAIATEX guide on verifying IECEx certificates and ATEX documents provides a broader identity check. For this article, the decision remains narrower: determine what ma, mb or mc says, then confirm that the entire encapsulated configuration and its evidence match the intended application.
A practical review sequence
First, the responsible designer defines the atmosphere, area classification, required EPL, group, temperature limits, ambient range and electrical duty. Next, procurement matches those inputs to the offered marking and ratings. The compliance review then checks the live certificate, schedule, conditions and instructions. The assembly designer verifies each component and interface before competent installers and inspectors confirm the installed configuration.
Do not accept a substituted encapsulated module, changed option or revised assembly merely because its headline suffix is unchanged. Product identity and controlled construction remain part of the evidence chain.
Current MMAIATEX certification status
The public MMAIATEX About page states that ATEX, IECEx and CCC certification work is in progress. MMAIATEX Explosion-proof Technology (Zhejiang) Co., Ltd. does not present this article, an encapsulation suffix, a standard reference, an IP rating, a product category or a representative photograph as proof that a particular product, component or assembly is certified.
Buyers must verify the exact legal manufacturer, model and suffix, full marking, current certificate status and scope, schedules, declarations where applicable, instructions, destination-market requirements and site conditions before selection or use.
Safety and legal disclaimer
This article provides general technical and procurement education. It does not select an EPL, classify a hazardous area, approve a material or construction, define fault behavior, authorize a component integration, certify an assembly or approve an installation. Competent parties must use the current licensed standards, exact certificate and schedule, controlled manufacturer instructions, site safety procedures and applicable law.
Request an encapsulation evidence review
Send the area classification, required EPL, electrical duty, proposed full marking, exact model, certificate and schedule, assembly drawing and destination market. MMAIATEX can identify available product information for review by the responsible designer, installer and compliance team.