The Ultimate Guide to Selecting the Right Gas Heater for Confined Spaces

When it comes to heating confined spaces, the selection of the appropriate gas heater is crucial to ensure safety, efficiency, and compliance with industry standards. Confined spaces, such as workshops, garages, or storage areas, pose unique challenges due to the potential risks of oxygen deficiency, explosive atmospheres, and the accumulation of harmful gases. This comprehensive guide will delve into the technical details and considerations to help you choose the best gas heater for your confined space application.

Understanding the Hazards of Confined Spaces

Confined spaces can present a variety of hazards that must be addressed when selecting and using a gas heater. These include:

  1. Oxygen Deficiency: Inadequate ventilation can lead to a decrease in oxygen levels, posing a serious risk to occupants. This can be caused by the displacement of oxygen by other gases or the consumption of oxygen during the combustion process.

  2. Oxygen Enrichment: Conversely, an excess of oxygen can also be dangerous, as it can increase the risk of fire and explosions.

  3. Flammable or Explosive Atmospheres: Confined spaces may contain flammable gases, vapors, or dusts, which can ignite and cause explosions if not properly managed.

  4. Toxic Gas Accumulation: The combustion of gas can produce carbon monoxide and other harmful gases, which can quickly build up in a confined space and pose a serious health hazard.

  5. Excessive Heat: Prolonged exposure to high temperatures in a confined space can lead to heat stress and other heat-related illnesses.

Selecting the Appropriate Gas Heater

what type gas heater to use in confined space

When choosing a gas heater for a confined space, it is essential to consider the specific hazards and requirements of the environment. Two primary options are:

1. Portable ATEX Heaters

Portable ATEX heaters are designed for use in hazardous areas and are certified to meet strict explosion-proof standards. These heaters can be placed directly inside the confined space or ducted to provide elevated ambient temperatures. Key features and specifications of ATEX heaters include:

  • Explosion-Proof Rating: ATEX heaters are certified to operate safely in potentially explosive atmospheres, with ratings such as II 2 G Ex db IIA T3 Gb or II 2 D Ex tb IIIC T200°C Db.
  • Combustion Air Source: ATEX heaters can be configured to draw combustion air from either the confined space or from an external source, depending on the ventilation requirements.
  • Heat Output: Typical heat output ranges from 10 kW to 60 kW, allowing for effective heating in a variety of confined space sizes.
  • Fuel Type: ATEX heaters are available for use with natural gas, propane, or other suitable fuels.
  • Safety Features: These heaters often include features like flame failure detection, overheat protection, and automatic shut-off mechanisms to enhance safety.

2. Direct-Vented Appliances

Direct-vented gas heaters are another option for confined spaces, as they take all their combustion air from the outdoors, preventing negative home pressures or thermal losses associated with traditional venting systems. Key characteristics of direct-vented appliances include:

  • Combustion Air Source: Direct-vented heaters draw all their combustion air from the outside, ensuring a steady supply of oxygen and preventing the introduction of potentially hazardous gases into the confined space.
  • Efficiency: These appliances are generally more efficient in their fuel utilization, as they do not experience the thermal losses associated with venting through walls or ceilings.
  • Heat Output: Direct-vented heaters typically range from 20,000 BTU/h to 50,000 BTU/h, making them suitable for a wide range of confined space sizes.
  • Fuel Type: Direct-vented heaters can be powered by natural gas or propane, depending on the available fuel source.
  • Safety Features: Many direct-vented models incorporate safety features like automatic shut-off, overheat protection, and carbon monoxide detection to enhance user safety.

Ensuring Proper Ventilation

Regardless of the gas heater type selected, proper ventilation is crucial to maintain a safe and comfortable environment in the confined space. This can be achieved through a combination of natural and mechanical ventilation methods:

  1. Natural Ventilation: Strategically placed openings, such as windows or vents, can allow for the natural exchange of air and prevent the buildup of harmful gases.

  2. Mechanical Ventilation: Fans, blowers, or ducting systems can be used to actively circulate and exhaust air from the confined space, ensuring adequate oxygen levels and preventing the accumulation of combustion byproducts.

When designing the ventilation system, it is essential to consider factors such as the size of the confined space, the heat output of the gas heater, and the potential for air stratification or dead zones. Consulting with a qualified HVAC professional can help ensure the ventilation system is properly sized and configured to meet the specific requirements of the confined space.

Safety Considerations and Monitoring

In addition to selecting the appropriate gas heater and ensuring proper ventilation, it is crucial to follow safety guidelines and manufacturer instructions. This includes:

  • Oxygen Level Monitoring: Portable gas detectors should be used to continuously monitor oxygen levels and ensure they remain within the safe range (typically 19.5% to 23.5%).
  • Toxic Gas Monitoring: Detectors for carbon monoxide and other harmful gases should be used to identify and address any potential accumulation of these substances.
  • Avoiding Unventilated Use: Gas heaters should never be used in confined spaces without adequate ventilation, especially when sleeping or in enclosed areas.
  • Compliance with Regulations: Ensure that the gas heater and its installation comply with all relevant local and national safety regulations, such as OSHA standards and building codes.

By following these safety guidelines and monitoring the confined space environment, you can help ensure the safe and effective use of gas heaters in these challenging environments.


Selecting the appropriate gas heater for a confined space is a critical decision that requires a thorough understanding of the potential hazards and the specific requirements of the application. Portable ATEX heaters and direct-vented appliances are both viable options, but the choice will depend on factors such as the size of the confined space, the available ventilation, and the specific safety concerns.

By carefully considering the technical details and safety considerations outlined in this guide, you can ensure that your confined space heating solution not only meets your heating needs but also prioritizes the safety and well-being of the occupants. Remember to always consult with qualified professionals and follow all relevant safety guidelines to ensure a safe and successful installation.