Is CO2 Flammable?

Carbon dioxide (CO2) is not flammable, and it doesn’t contribute to combustion. On the contrary – CO2 is one of the most widely used fire suppression agents in industrial and commercial settings.

In this guide, we’ll explore:

• Why carbon dioxide doesn’t burn
• How it works to extinguish fire
• How it’s used across industries

The Science Behind CO2’s Non-Flammability

Carbon dioxide is a completely oxidized carbon compound, meaning it has already undergone complete combustion. The carbon atom in CO2 is already bonded with two oxygen atoms in a stable configuration, leaving no capacity for further oxidation.

This molecular stability prevents CO2 from sustaining a flame or supporting combustion under normal conditions. The molecule cannot react with additional oxygen in the way that flammable substances do.

As for additional properties, CO2 is a colorless, odorless gas approximately 1.5 times denser than air. This density characteristic is especially important because it plays a crucial role in its fire suppression capabilities.

While carbon dioxide itself won’t burn, it’s important to note that under extreme conditions (temperatures exceeding 1,700°C or intense electrical discharges), CO2 can decompose into carbon monoxide and oxygen. Carbon monoxide is flammable, which should be kept in mind in specialized industrial environments.

How CO2 Works as a Fire Suppressant

Carbon dioxide extinguishes fires through two primary mechanisms that directly attack the fire triangle – fuel, heat, and oxygen.

First, it displaces oxygen in the immediate vicinity of the fire. By diluting the available oxygen below the concentration needed to sustain combustion (typically 15%), it effectively smothers the flame.

Second, the rapid expansion of CO2 during discharge produces a significant cooling effect. When liquid CO2 is released from a pressurized container, it rapidly expands and absorbs heat from the surrounding environment.

This dual action makes CO2 particularly effective for Class B fires (flammable liquids) and Class C fires (electrical equipment). The gas leaves no residue after discharge, which makes it ideal for:

• Sensitive electronic equipment
• Manufacturing facilities
• Any areas where cleanup from traditional extinguishing agents would be problematic

CO2 fire suppression systems are designed to rapidly displace enough oxygen to extinguish flames while following guidelines established by the National Fire Protection Association (NFPA 12). These systems can be designed for total flooding of an enclosed space or for local application directly onto a specific hazard.

Safety Considerations When Working With CO2

Despite its non-flammability, carbon dioxide comes with notable safety hazards that require proper management. The same property that makes CO2 effective for fire suppression – oxygen displacement – creates asphyxiation risks in enclosed spaces.

CO2 becomes dangerous at much lower concentrations than many realize. The NIOSH immediately dangerous to life or health (IDLH) concentration is only 4% (40,000 ppm), and OSHA’s permissible exposure limit is just 0.5% (5,000 ppm). Even at these lower concentrations, CO2 can cause dizziness, confusion, impaired judgment, and at higher levels, unconsciousness and death can occur rapidly without warning symptoms.

CO2 is heavier than air, so it can accumulate in low-lying areas, basements, and confined spaces. This characteristic calls for proper ventilation and monitoring in areas where the gas might be present.

Storage of compressed or liquefied CO2 presents additional hazards. Cylinders contain the gas at high pressure, creating potential risks if damaged or improperly handled.

Proper storage includes:

• Keeping cylinders secured in upright positions
• Ensuring they’re away from heat sources
• Putting protective caps in place when not in use

Regular inspection for corrosion or damage is essential for both safety compliance and reducing the risk of incidents.

To avoid accidents, personnel should be trained to recognize symptoms of carbon dioxide exposure and understand emergency evacuation procedures. Fixed detection systems and personal monitors provide additional layers of protection in high-risk environments.

Industrial Applications Leveraging CO2’s Properties

Many industries take advantage of carbon dioxide’s non-flammability for various applications beyond fire suppression.

In metal fabrication and welding operations, CO2 serves as a shielding gas that prevents oxidation during the welding process. Its relatively inert nature makes it ideal for creating controlled atmospheres around molten metal.

The food and beverage industry uses carbon dioxide extensively for:

• Carbonation (adding the fizz to drinks like sodas)
• Packaging (modified atmosphere packaging)
• Flash freezing

The non-flammable nature of CO2 ensures safety in food processing facilities where other potential ignition sources may be present.

In the oil and gas sector, CO2 is used for enhanced oil recovery, well acidizing, and as a fracturing agent. These applications rely on carbon dioxide’s ability to increase reservoir pressure and reduce oil viscosity without introducing flammability concerns.

Manufacturing facilities often use CO2 for cleaning precision parts and as a blasting medium for surface preparation. The dry ice form (solid CO2) sublimates directly from solid to gas, leaving no residue on sensitive components.

Take Advantage of CO2’s Non-Flammable Nature

Thanks to its non-flammability, CO2 is invaluable for numerous industries, particularly in fire suppression applications. 

Still, it’s crucial to keep its potential hazards in mind, especially the risks of asphyxiation risks. Through proper training, handling procedures, and engineering controls, carbon dioxide can be safely utilized to leverage its unique chemical properties across industrial, commercial, and medical settings.