Northern Air has a depth of experience designing HVAC systems for hazardous locations. This is a critical engineering challenge that demands a deep understanding of environmental risks, regulatory standards, and specialized equipment. These systems are essential in environments where flammable gases, vapors, dust, or toxic chemicals are present—such as chemical plants, oil refineries, pharmaceutical labs, and industrial manufacturing facilities.
Understanding Hazardous Locations
Hazardous locations are defined by the presence of substances that can ignite, explode, or cause health hazards. These include:
- Flammable gases and vapors
- Combustible dusts
- Corrosive chemicals
- Asphyxiants and toxic substances
The classification of these areas typically follows standards such as NFPA, OSHA, ATEX, and IECEx, which dictate the design and operational requirements for HVAC systems.
Most commonly, the source of the hazard is outside an enclosure – so that the HVAC system ensures that external components cannot cause ignition. However, some applications, such as battery houses, produce explosive gases requiring a different design philosophy – which is a suitable application for a custom Northern Air unit.
Although it’s critical to identify the proper standard, jurisdiction and classification, common industry terms are explosion-proof, classified and C1D2 (Class 1 Div 2).
Key Design Considerations
Explosion-Proof and Intrinsically Safe Equipment
HVAC systems in hazardous areas must incorporate components that prevent ignition:
- Encapsulated motors to contain sparks
- Explosion-proof conduits for wiring
- Intrinsically safe circuits that limit energy output
- Non-sparking materials like brass or copper alloys
These features are essential to prevent accidental ignition in volatile environments.
Positive Pressure and Purging
Proper ventilation is paramount. In addition to a properly designed damper and ducting system, the HVAC unit must maintain positive pressure to prevent ingress of hazardous
substances.
Pressure Monitoring and Control
Northern Air designs, programs and builds control panels with microprocessors for our units. When mounted inside a non-hazardous zone, a standard panel can safely operate the Explosion-proof HVAC system on the outside of a building. The purge and pressurization unit relies on an explosion-proof enclosure, which purges the interior of the building before the HVAC panel is energized.
Continuous pressurization utilizes differential pressure sensors to ensure that air is always flowing out of the building. Northern Air units communicate with the Gas and
Fire system in the building to indicate alarms.
Other Design Considerations
Some applications require HEPA or ULPA filters to trap fine particles and prevent dust explosions and corrosion resistant materials. Northern Air can customize the filtration system to match the needs of the application, and build with stainless steel, coated coils and powder coating to ensure longevity and safety.
Due to the severe consequences of a potential failure, many hazardous applications use an N+1 design, so that the system has redundancy. Northern Air is known for 24/7 continuous operation without failures, so our control system regularly switches between lead and lag units to cycle operation evenly.
Conclusion
HVAC design for hazardous locations is not just about climate control—it’s about life safety, regulatory compliance, and operational integrity. Northern Air leads the industry in explosion-proof HVAC design, by combining state-of-the-art manufacturing processes with the highest quality components. We create systems that protect both people and property in the most demanding environments.
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