IEC TS 60079-42 electrical safety devices: status and purpose
The official IEC TS 60079-42:2019 catalogue page identifies Edition 1.0, published on April 17, 2019. The IEC 60079:2026 series listing, published on July 23, 2026, still includes it. The 2026 stability date is a maintenance reference, not an expiry date or product approval. Control the applicable edition through the current catalogue, conformity route and project specification.
Part 42 is manufacturer guidance for electrical safety devices that control potential ignition sources in electrical or non-electrical Ex Equipment. It is not a certificate or a substitute for the applicable equipment and protection standards. The IECEx test report form for IEC TS 60079-42:2019 confirms the referenced edition but does not certify a product by itself.
What the safety function controls
The starting point is a potential ignition source in the Ex Equipment. The safety function acts on defined conditions so the source is less likely to become effective. IEC gives a sensor, logic system and final element as an example combination.
For procurement, treat that combination as one evidence chain:
- The sensor detects the defined condition.
- The logic system initiates the defined action.
- The final element puts the equipment into the intended state.
- Interfaces, power, settings and instructions preserve the offered function.
Not every design uses those labels or three separate products. Every necessary element must still be identified, assessed and controlled. One element's datasheet cannot establish the complete chain.
| Buyer question | Evidence that answers it | What does not answer it |
|---|---|---|
| Which ignition source is controlled? | Equipment assessment that identifies the source and the conditions that can make it effective | A generic alarm description |
| What performs the safety function? | Defined sensor, logic and final-element architecture with exact versions and interfaces | A photograph of one device |
| Which EPL claim depends on it? | Coordinated equipment assessment, applicable standards and conformity documents | An EPL label copied from another configuration |
| What happens during a fault or loss of power? | Controlled design analysis, response definition and instructions | An unsupported statement that the system is fail safe |
| How is the function maintained? | Commissioning, proof-check, inspection, repair and change-control requirements | A general maintenance schedule |
Scope limits buyers must not overlook
The IEC catalogue sets clear exclusions. IEC TS 60079-42 does not apply to mechanical control equipment such as pressure relief valves, mechanical governors or other mechanical safety devices. It does not apply to the use of gas detection. It also excludes control equipment intended to prevent an explosive atmosphere from occurring, such as inerting or ventilation systems, and it excludes explosion mitigation.
These exclusions distinguish different safety objectives. A detector used to warn of a gas release is not evidence for a Part 42 ignition-control function. The MMAIATEX IEC 60079-29-0 gas detection equipment guide explains that separate family. Atmosphere-prevention controls and explosion-mitigation systems require their own engineering and legal basis.
The ISO 80079-36 non-electrical Ex equipment guide explains the non-electrical ignition-hazard route. An electrical function can control a source in non-electrical Ex Equipment, but the equipment still needs its applicable ISO 80079 assessment.
Why a safety device does not automatically increase EPL
IEC states that a safety device can be a measure used to achieve the required EPL with respect to a potential ignition source. It also states that increasing the EPL of Ex Equipment by simply adding a safety device is outside the scope of the Technical Specification.
An EPL applies to the equipment and assessed protection, not to a list of parts. The manufacturer must evaluate the ignition source, construction, operating modes, foreseeable faults and relevant protection standards as a combination. Use the MMAIATEX EPL guide to understand Ga, Gb, Gc, Da, Db and Dc, but not to assign an EPL to a product.
An IP rating can support an enclosure requirement, but the IP66 versus explosion-proof guide explains why it cannot demonstrate a safety function, EPL or Ex certification.
Seven-step buyer evidence sequence
1. Define the equipment and ignition source
Record the legal manufacturer, exact model, function, protection concept, group, intended EPL, temperature information, ambient range and modes. Identify the potential ignition source and the conditions that can make it effective.
2. Map the complete safety-function chain
Identify every sensor, logic element, final element, interface, power supply, setting and communication path. Record controlled hardware and software revisions. Confirm whether the device was assessed independently or only with specified Ex Equipment.
3. Establish the defined response
Define the initiating condition, action, controlled state and operating assumptions. Include start-up, shutdown, bypass, reset, power loss, disconnected inputs and relevant diagnostics. Do not invent acceptance values from a general article.
4. Trace the EPL claim to the combination
Request the assessment connecting the ignition source, required EPL, safety function and equipment standards. Confirm that the offered configuration matches. A higher-rated device does not raise the surrounding equipment's EPL by itself.
5. Verify conformity records and restrictions
Check the legal manufacturer, model, issue, scope, status, schedule, special conditions and instructions in the relevant official system. The MMAIATEX guide to verifying IECEx certificates and ATEX documents provides a document workflow. The IEC reference on a datasheet or an IECEx test report form is not a certificate.
6. Control commissioning and maintenance
Obtain instructions for installation, settings, checks, inspection, maintenance, fault response and replacement. The required task and interval must come from the controlled design, manufacturer instructions, applicable standard and site controls.
7. Put every change through review
Control substituted sensors, revised logic, changed setpoints, firmware, relays, wiring, bypasses and process changes. Reassess the ignition source and complete function before acceptance. Electrical compatibility does not prove the protection basis remains valid.
Relationship with general Ex equipment requirements
IEC 60079-0:2026 specifies general construction, testing and marking requirements for Ex Equipment and Ex Components. Its publication page says other documents supplement those general requirements. Part 42 addresses a specific safety-function approach and does not replace Part 0 or the relevant type-of-protection standard.
Connect safety-device evidence to the exact equipment marking, certificate schedule, drawings, instructions and protection documents. Verify area classification, installation design and destination rules through competent parties. This guide cannot perform the manufacturer assessment or approve an installation.
Current MMAIATEX certification status
MMAIATEX is the public brand of MMAIATEX Explosion-proof Technology (Zhejiang) Co., Ltd. The public About page states that ATEX, IECEx and CCC certification work is in progress. This article, a product image, a standard reference, an IP rating or a safety-device datasheet does not prove that a particular MMAIATEX product or combination is certified. Verify exact-model marking, current documents, scope, conditions, interfaces and destination requirements before selection.
Safety and legal disclaimer
This article is general technical information, not a safety-function assessment, ignition-hazard assessment, certificate, area classification, installation approval, commissioning procedure or legal opinion. An ineffective ignition-control function can contribute to fire, explosion, injury or death. Use licensed current standards, exact equipment documents, applicable law and competent professionals. Stop work if the ignition source, required EPL, device configuration, response, fault behaviour, evidence scope or maintenance basis is uncertain.
Contact MMAIATEX for an evidence request
Send the equipment model, identified ignition source, required EPL, area classification, safety-function architecture, offered device versions, operating conditions, destination and required document list so MMAIATEX can organise available product information for competent review.