Inside the spark zone: condition monitoring best practices for hazardous locations

An ignition starts small. A bearing on a motor shaft begins to wear, creating friction that steadily raises internal temperatures. Over time, vibration increases, insulation weakens and the conditions for an internal spark begin to build. All of this unfolds inside the equipment, hidden from view, before anyone on the floor notices anything is wrong.

In a typical industrial environment, these early signs of stress may lead to equipment damage or unplanned downtime. In hazardous locations or explosive atmospheres, the story can end very differently. When flammable vapors, gases or combustible dust are present, a spark that would have been inconsequential suddenly becomes the ignition source. When this occurs in an explosive environment, an internal fault can now escalate with alarming speed and significant damage.

With this in mind, condition monitoring for equipment used in hazardous environments takes on a dual purpose:

• Equipment must reliably detect the early indicators of equipment degradation
• Equipment must be engineered so that, should a fault occur inside the device, it does not ignite the atmosphere around it

Performance and protection must work together.

Four best practices for using condition monitoring in hazardous locations

For manufacturers and facility owners, this dual purpose creates a specific set of considerations when designing, selecting or deploying condition monitoring equipment in hazardous environments.

1. Understand the equipment’s environment

First, identify any workplace areas where an explosive atmosphere is present—or could be present. Hazardous (classified) locations are defined by how often vapors, gases, or combustible dust are likely to occur: continuously, occasionally, or only under abnormal conditions.

Whether the North American Class/Division system or the international Zone system are applicable, the resulting area classification is one of the factors that goes into determining the device’s protection method (explosion-proof/flameproof or intrinsically safe), and certification requirements.

Looking at the environment at a gasoline station offers a clear example. Vapors from the underground tank are continuously present. Around the pump, vapors appear mainly during refueling. Within a small radius of the pump, vapors may occasionally be present under abnormal conditions. Beyond that, the atmosphere is not considered ignitable. Each of these spaces carries a different classification. This example holds true – and the potential for damaging fire and explosion increases exponentially – when translated into highly combustible environments such as those found within oil and gas refineries, manufacturing plants, pharmaceutical facilities, and other hazardous locations.

This principle applies everywhere: The likelihood of an atmosphere being explosive determines the required protection level.

Condition monitoring equipment must be designed and certified for the correct hazard classification. Facility owners, in turn, must verify that sensors — whether a temperature probe, vibration monitor or gas detector — match the precise hazard level where they are installed. A device built for one environment may be unsafe, noncompliant, or ineffective in another.

2. Ensure equipment is certified for performance and hazardous location protection

For condition monitoring systems and safety-related systems, it is not sufficient for a device to be safe to install in hazardous locations. The device must also reliably perform the monitoring function for which it was designed. Without performance testing, there is no confirmation that the equipment will detect the very conditions that could lead to ignition.

Industrial refrigeration systems often have a machine room that contains compressors, condensers, and flammable refrigerants, such as ammonia. FM requires a flammable gas detector to be installed in that room. The detector must be installed properly and must reliably detect an ammonia release under cold, humid, and vapor-dense conditions.

Many certification bodies evaluate these two concerns separately, issuing one mark for hazardous location compliance and another when the performance validation is included. In these applications, FM Approvals does not separate the two and will not issue a certification unless both criteria are met.

In ammonia refrigerator systems, for example, an enclosed freezer room often contains flammable refrigerant, confined spaces, and compressors. FM Approvals requires a flammable gas detector in that room. The detector must be installed properly and reliably detect an ammonia release under cold, humid, and vapor-dense conditions.

For manufacturers, this dual evaluation reduces ambiguity. For operators, it ensures that equipment in hazardous locations is both safe and effective.

3. Look for equipment tested under real-world industrial conditions

Condition monitoring equipment in hazardous locations must remain functional in environments that routinely degrade performance. FM Approvals Examination Standards evaluate a device’s ability to maintain accuracy and reliability under:

• Extreme temperatures
• Long-term vibration
• Humidity and condensation
• Chemical exposure or corrosive vapors
• Contaminants and particulate buildup
• Mechanical shock
• Electromagnetic interference
• Extended service intervals

These factors often appear together in hazardous environments. A vibration sensor installed on a refinery pump, for example, must distinguish between normal equipment vibration and early signs of bearing wear — while surrounded by heat, chemical vapors and constant mechanical stress. Performance testing ensures the device continues to function even under less-than-ideal conditions.

4. Verify equipment meets all required regional and international certifications

Different regions follow different hazardous-location schemes (NEC/CEC in North America, ATEX in Europe, IECEx internationally), and equipment may need to comply with more than one. FM Approvals simplifies this process by using a single testing program that evaluates ignition protection and maps those results across all major global certification schemes. This reduces the need for duplicate testing, speeds up market access for manufacturers, and ensures that facility owners can source the same FM Approved equipment across all their global locations.

Protecting continuity for facilities and equipment

Condition monitoring in hazardous locations is fundamentally about preventing ignition. But preventing ignition requires more than placing a sensor in a classified area and trusting it won't spark. It requires equipment that:

• Is appropriate for the classification of the environment
• Uses the correct ignition-protection method
• Meets certification requirements across all jurisdictions
• Performs reliably in real-world industrial conditions
• Has been tested to ensure it will do the job it was designed to do

FM Approvals’ approach of evaluating both performance and ignition protection within a single testing program helps manufacturers bring reliable, globally accepted products to market and gives facility owners confidence that the equipment can detect problems early and function in hazardous environments.

Visit fmapprovals.com to learn more about the products we certify and our Examination Standards. To find all FM Approved products, visit the Approval Guide where product listings, engineering data and technical information can be found. If your organization manufactures property loss prevention products and would like to begin the certification process, apply for certification or find an FM Approvals office near you.