Predictive Maintenance in Hazardous Environments: A Complete Guide

Key Takeaways

• Hazardous area classification (NEC Class/Division in North America, IEC/ATEX Zone elsewhere) determines which equipment, including monitoring sensors, is legally permitted to operate in locations where an explosive atmosphere may exist.
• Manual inspection rounds sit at the weak end of NIOSH’s hierarchy of controls (an administrative control). Continuous monitoring removes the need for a person to enter the zone at all, functioning like the engineering controls that the hierarchy ranks as more effective.
• Wireless, intrinsically safe sensors don’t require conduit or wiring, so installation doesn’t trigger the hot-work permit process that a hardwired sensor would, and it doesn’t require a shutdown.
• Certification isn’t a blanket guarantee. Every certified device has real operating limits (maximum ambient temperature, specific atmosphere ratings), and those limits should be checked against the actual site, not assumed from a general “hazardous-rated” label.
• Oil and gas carries the largest share of this market, but chemical, mining, food and beverage, and other industries face the same underlying coverage gap.
• A Middle Eastern petrochemical manufacturer saw ROI of nearly 4X within six months of deploying continuous monitoring, with maintenance costs down as much as 72% and over 1,800 hours of downtime avoided, evidence that the safety case and the business case point in the same direction.

Predictive maintenance in hazardous environments has always been more complex than selecting a certified sensor. Hazardous-area classifications, installation requirements, regulatory standards, network architecture, and maintenance practices all influence how condition monitoring is deployed. Together, they’ve limited where continuous monitoring could be applied and how broadly it could scale.
Those constraints are changing. Certified wireless technologies and modern monitoring platforms are making it more practical to extend continuous condition monitoring to equipment that has historically relied on periodic inspection routes, without requiring a complete overhaul of existing infrastructure.

The global hazardous-area equipment market reflects that shift: Fortune Business Insights estimates it will grow from $15.79 billion in 2026 to $26.60 billion by 2034, driven by industrial expansion, stricter safety requirements, and increased adoption of connected monitoring technologies. As more facilities modernize their reliability programs, hazardous-area assets are becoming part of that broader strategy rather than a separate exception. 

This guide explains how predictive maintenance works in hazardous environments, which hazardous-area requirements shape deployment decisions, and what to evaluate when selecting a monitoring solution.

What makes an environment hazardous?

According to OSHA’s standard on hazardous (classified) locations (29 CFR 1910.307), a hazardous area is a location where flammable gases, vapors, or combustible dust may create an explosive atmosphere. Those conditions determine which equipment can be installed, how it’s certified, and how maintenance activities are performed. For condition monitoring, hazardous-area classifications influence everything from sensor selection to installation methods and ongoing maintenance practices.

Hazardous environments generally fall into two categories: flammable gases and vapors, or combustible dust. While industries vary, the monitoring challenge is consistent. Whether it’s a refinery compressor, a grain elevator fan, or a dust collection blower, reliability teams need continuous visibility without introducing new safety risks or adding unnecessary access requirements.

Industries and Assets Most Affected

Hazardous area classification applies wherever a facility handles flammable gases, vapors, or combustible dust as a part of normal operations. Hazardous areas tend to be concentrated in a handful of industries. Fortune Business Insights breaks down the global hazardous area equipment market by end industry, and oil and gas leads by a wide margin. Oil and gas is projected to hold roughly 32% of the global market in 2026, driven by the flammable hydrocarbons present throughout upstream and downstream operations, from wellheads and compressor stations to refineries and tank farms. That concentration is exactly why oil and gas predictive maintenance use cases dominate this space: the sheer number of hazardous-duty assets in a single facility means the coverage gap compounds fast.

Food and beverage manufacturing is set to grow steadily in this space too, largely because of the combustible dust risk. Flour, sugar, and starch handling all generate fine particulates that meet the same classification triggers as a gas leak, even though it doesn’t look like one. Chemical and pharmaceutical manufacturing carries similar exposure, driven by flammable solvents and reactive process chemistry. Mining and energy and power round out the largest segments: mining from methane and coal dust in underground and processing operations; and energy and power from a mix of fuel handling and combustion processes. 

Across these industries, the equipment that carries the actual exposure tends to be the same category of rotating assets: pumps, compressors, agitators, fans, and blowers. A refinery’s compressor and a grain facility’s dust collector fan look nothing alike, but they’re both classified equipment for the same underlying reason with the same monitoring problem: they’re hard to reach, hard to take offline, and historically hard to keep continuous eyes on.

Why Standard Monitoring Fails in Hazardous Zones

Most hazardous-zone monitoring today runs on manual inspection rounds. NIOSH’s hierarchy of controls ranks that approach as an administrative control, among the least effective methods in the framework. The stronger alternative is continuous, certified sensing, an engineering control that removes the hazard by design instead of relying on a person doing everything right. But standard sensors are themselves a potential ignition source, which has historically made that option expensive and a potential safety hazard to install.

So manual rounds remain the default: the regular technician gets the right permit, puts on the right PPE, and walks a route on a schedule to take a reading. That technician knows the equipment. But when they’re not available, whoever fills in doesn’t always have that same hands-on familiarity. Fred Wasden, a former Shell operations leader who also led the company’s U.S. Health, Safety and Environment (HSE) department, has traced incidents from his experience in these zones back to that gap.

There’s also a shelf-life problem with the manual reading itself. Whatever a route catches is only as current as the last walk-through, which means a fault that develops between rounds runs unchecked until the next scheduled visit, sometimes days or weeks later.

The equipment side of the problem compounds this. A standard wired vibration sensor is itself a potential ignition source. Putting one in a Class 1 Division 1 or Zone 1 area means using explosion-proof, certified hardware run through conduit that has to be installed without shutting down an operating unit. That’s historically been expensive and disruptive enough that many facilities have gone without, defaulting to manual rounds.

The cost of that default shows up when something actually fails. Wasden has described hazardous-zone repairs running several times more expensive than an equivalent repair elsewhere, with planning alone taking three to four times longer. In hydrocarbon operations, a single offline production unit can mean on the order of a quarter million dollars an hour in deferred revenue while that planning happens. These aren’t published industry benchmarks. They’re numbers Wasden watched play out firsthand.

Manual rounds also carry a workforce cost. Working safely in a classified area requires its own certification, one that not every available technician holds. (IECEx, for instance, runs a Certification of Personnel Competencies Scheme specifically for people working in explosive atmospheres.) That requirement narrows the pool of people who can do this work. Every hour they spend walking routine inspection routes is an hour they can’t spend on work that requires their expertise.

Together, high installation costs and a weak fallback produce the coverage gap this guide opened with. For real-world numbers on how plants have closed that gap by eliminating manual rounds, see Hazardous Zone Monitoring: How Always-On PdM Reaches Your Most Dangerous Assets.

What Continuous Monitoring Looks Like in a Hazardous Environment

Continuous condition monitoring in a hazardous environment works through sensors that capture vibration, temperature, and other signals around the clock. On their own, those readings are just raw signal, not something a maintenance team can act on directly. AI-driven diagnostics are what turn that signal into an actual finding: a specific developing fault, on a specific asset, with enough lead time to plan a response before it becomes a failure. The hardware itself can’t be an ignition source, so it has to be certified accordingly. Additionally, it must transmit its data without running wires through the classified zone.

Wireless, intrinsically safe sensors are what make that possible at scale. Because they are certified for the classified area and don’t require a conduit or hardwired connection back to a control room, installing them doesn’t require a shutdown. It also doesn’t trigger the same hot-work permit process a wired install would.

The sensors themselves typically capture three-axis vibration, surface temperature, and magnetic flux, transmitting over an encrypted connection to a nearby gateway. Line-of-sight transmission range commonly runs to several hundred feet. Dense equipment, structures, or scaffolding in a real plant environment can reduce that range, which is why a site survey, not a spec sheet number, determines how many gateways a given facility actually needs. Battery life on purpose-built hazardous zone sensors is measured in years rather than months, which matters more here than on a standard asset: changing a battery means suiting up and re-entering the classified zone, so hardware that needs frequent battery swaps reintroduces the safety exposure the whole system is meant to remove.

A busy industrial environment is mechanically and electromagnetically noisy, so it’s fair to ask whether that noise drowns out a useful signal. Modern diagnostic platforms handle this by analyzing machine-specific feature sets rather than raw amplitude alone, using known equipment geometry (bearing specifications, rotational speed, and similar metadata) to isolate the frequencies that actually matter for that particular asset and filter out background vibration from neighboring equipment. That’s a meaningfully different approach than a simple threshold alarm, and it’s why this kind of diagnostic can work reliably in environments that would overwhelm a threshold-based sensor with false alarms.

Certification Landscape

Hazardous area classification is the process of categorizing a location by how likely an explosive atmosphere is to be present, and it’s what determines which electrical equipment, including monitoring sensors, is legally allowed to operate there. Two parallel systems govern this worldwide. Some multinational operators need to work with both at once. Knowing which system applies to your facility is the first practical step in evaluating any monitoring solution.

NEC Hazardous Area Classification (Class/Division)
North America uses the Class/Division system defined in NEC Article 500, part of the National Electrical Code (NFPA 70). Class I covers flammable gases and vapors. Class II covers combustible dusts. Within each Class, Division 1 means the hazard is likely present during normal operation. Division 2 means it’s only present under abnormal conditions, like a seal or gasket failure. NFPA 497 hazardous area classification guidance is the companion recommended practice most facilities actually use to classify Class I gas and vapor areas, since it supplies the specific ignition and flammability data for individual chemicals that the classification decision depends on.
Hazardous Area Classification Zones, Explained (IEC/ATEX)

Most of the rest of the world follows IEC hazardous area classification standards, specifically IEC 60079 (the basis for the EU’s ATEX directive), which classify areas by Zone instead. Zone 0, 1, or 2 apply to gases, based on how continuously an explosive atmosphere exits. Zone 20, 21, or 22 apply to the dust equivalent. Equipment certified under this system carries and IECEx mark. IECEx is the international scheme operated by the IEC, and it lets a single certificate be recognized across dozens of member countries rather than requiring separate national approval in each one. The two systems map roughly, not exactly, onto each other. Class I Division 1 is comparable to Zone 0/1, and Division 2 lines up closer to Zone 2. But a facility operating under one system can’t assume equipment certified under the other transfers over cleanly.

That mapping matters because certification markings themselves are dense. A single string like “II 1G Ex ia IIC T4 Ga” encodes the equipment group, protection method, gas group, and temperature rating all at once. Reading one correctly is a real skill a plant manager needs.
It’s worth being direct about something that’s easy to gloss over in a sales conversation: certified hardware still has real operating limits. A device rated for hazardous gas atmospheres up to 70 degrees Celsius ambient temperature isn’t rated above that. A device with no rating for acidic environments shouldn’t be installed in one regardless of its other certifications. Any vendor’s certification should specify that exact envelope. Equipment installed further from the point of release often carries a lower-tier rating than the sensors themselves, Zone 2 or Division 2 rather than Zone 0/1 or Division 1. A gateway that collects data from sensors but doesn’t sit directly on the process equipment, is a typical example. That is normal and appropriate given its placement, not a sign of a weaker overall system.

The Business Case: Safety, Uptime, and Compliance Together

A failure in a classified area carries costs a normal area failure doesn’t, beyond the repair itself. When an incident in a hazardous zone results in an injury, it becomes a recordable event under OSHA’s injury and illness recordkeeping rule (29 CFR 1904), which can trigger inspection activity. That’s before accounting for the deferred-production cost, or the possibility of environmental exposure if the failure involves a release. Safety, regulatory standing, uptime, and environmental risk move together here, not against each other. The strongest business case treats them as one argument, not four.

One deployment shows what that looks like in practice. A Middle Eastern petrochemical manufacturer piloted continuous monitoring in 2021, after years of relying on manual routes and portable data collectors. The facility runs more than 50 processing units, everything from crude distillation to power generation. Within six months, the head of maintenance reported ROI of nearly four time the investment on repair savings alone, and noted that including downtime avoidance would make that figure “much, much higher.” Maintenance costs across the monitored assets have dropped by up to 72% since, and the program has avoided more than 1,800 hours of machine downtime. Individual catches have ranged from a $30,000 pump repair flagged early to a single overnight compressor alert that avoided $300,000 in costs and more than 200 hours of downtime.

What that example shows is the underlying shift continuous monitoring makes possible. The maintenance team gets enough lead time to plan the repair on their own schedule, with the right parts and the right people. Reacting to an unplanned trip in a hazardous zone is a harder, riskier option.

How to Evaluate a Hazardous Monitoring Solution

Evaluating a hazardous-zone monitoring solution comes down to a checklist: reviewing a vendor’s specific claims against verifiable evidence, rather than taking a general “hazardous-rated” or “certified” label at face value. You don’t need to be a certification expert. You just need to know which questions have a specific answer, and notice when a vendor gives you a general one instead.

Certifications. Ask which classification system the equipment is certified under: NEC Class/Division, ATEX/IEC Zone, or both. Confirm the specific division or zone, gas or dust group, and temperature code match your facility’s actual classification. Ask to see the certificate itself.

Operating limits. Every certified device has a real operating envelope: a maximum ambient temperature, and often exclusions for specific atmospheres like acidic environments. 

Installation footprint. Does deployment require conduit, hardwiring, or a shutdown? Or can it happen during normal operation without triggering a hot-work permit process?

Sensor coverage. Is the hardware capturing multiple signal types or just one? Single-signal monitoring misses fault modes that a broader sensor set would catch.

Personnel requirements. Who’s qualified to install, maintain, and interpret this system? Is that person also the one you’d need for an actual emergency?

Platform unification. Does hazardous-zone data live in the same system as the rest of the plant’s monitoring, or in a separate tool that only a few specialists know how to use? Better sensors don’t translate into better visibility if systems are siloed, since the data won’t reach the people who need it.

Data security. Is data transmission encrypted, and can the vendor produce documentation aligned with recognized industrial cybersecurity practices? IEC 62443 is the standard specifically written for industrial automation and control system security. This matters more in a hazardous-zone deployment since these systems often touch process-critical infrastructure.

Deployment speed. What’s the actual time from decision to assessed equipment health, in days, not quarters? Ask whether the vendor commits to a specific timeline before or after the sale, and whether that answer changes if a reseller or hardware partner is handling the installation. Some vendors have more visibility and control over one channel than another.

See It on Your Assets

Everything covered in this guide comes down to one practical question: what does closing this gap actually look like for your business?

It starts with your team gaining greater control over hazardous-zone assets with continuous monitoring. Using Augury’s Machine Health Hazardous solution, your team benefits from:

• Baker Hughes’ Ranger Pro sensor, certified to Class I/II Division 1 and matching ATEX/IECEx ratings, capturing continuous vibration, temperature, and magnetic flux readings
• Diagnostics that read machine-specific feature sets rather than raw signal amplitude, so alerts reflect real developing faults instead of background noise
• Wireless data collection from many sensors at once (via the Cordant Edge Gateway), so adding coverage doesn’t mean running new cabling for every device

Installation doesn’t require conduit runs or hot work permits, and security is enterprise-grade (X.509 device authentication and 128-bit AES encryption) with no extra work on your end.

If your hazardous-zone assets are still running on manual rounds, we can help you change that.
Talk with an expert

Resources & Further Learning

Related Reading

Hazardous Zone Monitoring: How Always-On PdM Reaches Your Most Dangerous Assets 

Fault Detection and Diagnostics: The Foundation of Reliable Operations (This guide is for readers whose interest extends beyond hazardous-zone assets to fault detection and diagnostics generally.)

Tools

Value Calculator Estimate the potential impact of continuous monitoring on your own assets

Watch

Full webinar: From Hot Work Permits to Continuous Coverage

FAQs

• Is a “hazardous area” the same as a general chemical hazard?

  Hazardous area classification and general chemical hazard classification are two different systems, though the distinction is genuinely useful going into a vendor or audit conversation. OSHA’s Hazard Communication Standard classifies chemicals themselves into physical, health, reactive, and other categories for labeling purposes. Hazardous area classification is a separate, narrower system that governs physical locations where an explosive atmosphere may exist, and determines which equipment can be installed there. Knowing which framework a conversation is actually about is often the fastest way to get a useful answer.

• How do ATEX and IECEx certifications differ?
  

  ATEX and IECEx are two different certification systems for equipment used in explosive atmospheres. ATEX is a European Union regulatory directive, legally required for equipment sold or used in EU member states. IECEx is a voluntary international certification scheme, recognized in more than 30 member countries, built on the same underlying IEC 60079 standards ATEX also draws from. In practice, equipment often carries both markings side by side, since IECEx recognition can streamline the path to certification in additional countries beyond the EU. Neither one substitutes for the other where it’s specifically required by law.

• What is the US equivalent of ATEX certification?

  The US has no direct one-to-one equivalent to ATEX certification, because the US uses a different regulatory mechanism entirely. Rather than a single certification like ATEX, OSHA requires that electrical equipment in classified areas be certified by a Nationally Recognized Testing Laboratory (NRTL), organizations like UL, MET, Intertek, or CSA. That certification has to match the applicable Class/Division standards in NEC Article 500. Several of the same labs that issue ATEX and IECEx certificates also hold NRTL status, and OSHA has increasingly accepted NRTL-issued certifications based on the IEC 60079 series. Still, an ATEX certificate on its own doesn’t satisfy US requirements. Equipment intended for US installation needs its own NRTL listing.

• Is IECEx certification accepted in the USA?

  IECEx certification is not a direct substitute for US certification. Equipment installed in the US still needs NRTL certification under OSHA’s program, regardless of whether it also carries an IECEx mark. That said, the practical gap is smaller than it sounds. Many NRTLs (UL and MET among them) are also accredited IECEx certification bodies, and they often test equipment against harmonized programs that produce both certifications from largely the same underlying evaluation. A vendor with both marks has typically already cleared most of the technical bar for either market.

• What is the difference between Class I Division 1 and Zone 1 for industrial sensors, and is Zone 1 the same as Class I Division 1?

  Class I Division 1 and Zone 1 both describe the same basic situation, a location where an explosive atmosphere is likely present during normal operation, using two different classification frameworks. Division 1 comes from the NEC/CEC system (NFPA 70) used in North America. Zone 1 comes from the IEC/ATEX system used across most of the rest of the world. They aren’t a clean one-to-one match, so equipment certified for one system isn’t automatically certified for the other.

• Is C1D2 the same as ATEX?

  C1D2 (Class I, Division 2) and ATEX are not the same, though they describe a similar level of risk. Class I, Division 2 (C1D2) is the North American classification for an area where flammable gas or vapor is present only under abnormal conditions, like an equipment failure or leak. Its closest ATEX/IEC equivalent is Zone 2. But they come from different regulatory systems with different testing and marking requirements, so C1D2-certified equipment isn’t automatically Zone 2 certified.

• What is the difference between hazardous Zone 1 and hazardous Zone 2?

  Hazardous Zone 1 and Zone 2 both describe locations where an explosive gas or vapor atmosphere is a real possibility, but they differ in how often. Zone 1 means the hazardous atmosphere is likely present during normal operation, for continuous periods or on a regular basis. Zone 2 means it’s not normally present, and would only show up briefly, typically from an accidental release or equipment fault. That distinction drives real equipment differences. Zone 1 requires the highest level of certification, since equipment there has to withstand routine exposure. Zone 2 equipment can often use a lighter-duty protection method, since it only has to hold up under an abnormal, short-duration event. On a real installation, this is often why sensors mounted directly on hazardous-duty equipment carry a Zone 1 (or higher) rating, while supporting hardware sited slightly further from the source, like a gateway or junction box, can carry the less stringent Zone 2 rating instead.

• What is Class I Division 2, Group C and D?

  Class I, Division 2, Group C and D is a specific hazardous-area classification describing a location where flammable gas or vapor from Group C materials (ethylene, and similar) or Group D materials (propane, gasoline, and most common industrial hydrocarbons) is present only under abnormal conditions, such as a seal failure or accidental release, rather than during normal operation. Groups C and D are among the least restrictive gas groups compared to Groups A (acetylene) and B (hydrogen), since C and D materials generally require more energy to ignite. But “Division 2” and “Group C/D” are two separate pieces of the classification, describing likelihood and material type respectively. Both have to match for equipment to be correctly rated for a given location.

• What NEMA rating is Class I Division 2?

  Class I, Division 2 describes an area where flammable gases or vapors are not normally present, but could become hazardous under abnormal conditions. Because the classification describes the environment rather than a specific type of enclosure, there isn’t one NEMA rating that applies to every Division 2 installation. Division 2 areas can use different protection methods depending on the application: nonincendive equipment is one option specifically permitted for Class I, Division 2, while explosion-proof equipment can also be used when appropriately approved. NEMA Type 7 is an enclosure type for Class I hazardous locations, but it isn’t synonymous with Class I, Division 2. The right equipment choice depends on the area classification, the equipment being installed, and the protection method being used.

• What is the OSHA limit for the Lower Explosive Limit (LEL)?

  OSHA’s permit-required confined spaces standard (29 CFR 1910.146) sets the relevant threshold: an atmosphere is considered hazardous once flammable gas, vapor, or mist concentration reaches 10% of the Lower Explosive Limit (also called the Lower Flammable Limit, or LFL). This isn’t a universal hazardous-area classification rule; it’s specific to the confined spaces standard. Below that threshold, the atmosphere isn’t necessarily safe. Measurable flammable vapor below 10% LEL can indicate a leak that’s building toward a hazardous concentration, but it isn’t yet classified as an immediate flammability hazard under that standard. This threshold is a big part of why continuous gas monitoring exists as its own discipline alongside the equipment-classification and condition-monitoring topics covered elsewhere in this guide.

• What is predictive maintenance in the oil and gas industry?
  

  Predictive Maintenance in the oil and gas industry is the use of continuous or near-continuous condition data, vibration, temperature, and similar signals, to catch developing equipment faults before they cause unplanned downtime, rather than relying on fixed-interval inspections or waiting for a failure. In hazardous-duty oil and gas assets specifically, it also removes the safety exposure of sending someone into a classified area to collect that data manually.