What CO2 Is Used For in Cars

CO2 is mostly a regulated exhaust emission from combustion engines, but it also has deliberate roles: it is used as an automotive refrigerant (R-744) in some air-conditioning and heat-pump systems, appears in cabin air-quality sensing on select models, serves as a fire-extinguishing agent and tire-inflation source in certain use cases, and is widely used around cars in manufacturing, cleaning, and leak testing. Beyond the vehicle itself, captured CO2 is increasingly a feedstock for synthetic “e-fuels.” This article explains where CO2 is intentionally used in and around cars today, how that’s changing under new regulations, and what it is not used for.

Where CO2 shows up beyond tailpipes

While drivers most often hear about CO2 as a greenhouse-gas emission measured and regulated by governments, there are practical, intentional uses for carbon dioxide in automotive technology and the broader ecosystem that builds and services vehicles. Below are the principal areas where CO2 is purposefully involved.

• As a refrigerant (R-744) in some vehicle HVAC and heat-pump systems, especially in certain European applications and in buses, thanks to its very low global-warming potential and strong low-temperature performance.
• In cabin air-quality management, where select modern vehicles use CO2 sensors to decide when to bring in fresh air and to reduce driver drowsiness risks during heavy recirculation.
• In portable fire extinguishers (and some specialized suppression systems), particularly in motorsport and certain fleet or aftermarket setups.
• For portable tire inflation and on-board air in off-road communities, which sometimes use CO2 tanks for fast, high-volume inflation and pneumatic tools.
• In manufacturing and service: as a shielding gas for welding, for dry-ice (solid CO2) cleaning of parts and paint surfaces, and as a tracer/calibration gas for leak detection and HVAC service.
• In the fuel supply chain: captured CO2 is combined with green hydrogen to synthesize e-fuels compatible with existing internal-combustion engines.

Together, these uses span in-vehicle technologies, workshop practices, and the emerging low-carbon fuel landscape—distinct from CO2’s role as a tailpipe emission.

Deliberate uses inside passenger vehicles

CO2 as an automotive refrigerant (R-744)

CO2 is used as the refrigerant R‑744 in some car and bus HVAC systems. It has a global-warming potential (GWP) of 1, excellent heat-pump performance in cold climates, and avoids PFAS concerns tied to some fluorinated refrigerants. Although most new light-duty vehicles currently use R‑1234yf (GWP ~4), R‑744 is deployed in certain models and is increasingly common in European city buses and in heat-pump systems for electrified vehicles where cold-weather efficiency matters.

Key considerations explain this gradual but growing deployment:

• Regulatory drivers: The EU Mobile Air-Conditioning (MAC) Directive bans high-GWP refrigerants in new cars, and the updated EU F-gas rules (adopted in 2024) accelerate the phase-down of fluorinated gases, nudging industry toward natural refrigerants like CO2.
• Thermal performance: CO2 heat pumps can deliver robust cabin heating at low ambient temperatures, helpful for EV range preservation in winter.
• Engineering trade-offs: CO2 systems operate at higher pressures and require different components and service tools, which has slowed mass adoption in light vehicles compared with buses and commercial fleets.

In short, R‑744 is not yet universal in cars, but its role is growing where climate performance and future regulatory alignment are priorities.

Cabin air-quality management

Some newer vehicles integrate CO2 sensors into their climate-control logic. When cabin CO2 levels rise during extended recirculation—common in heavy traffic or tunnels—the system can increase fresh-air intake to keep occupants alert and comfortable. This feature appears mainly on higher-trim or newer European models and complements PM2.5 particle sensing.

Onboard safety and convenience equipment

CO2 also appears in certain automotive-adjacent gear carried in or on vehicles:

• Fire extinguishers: CO2 extinguishers are used in workshops and motorsport paddocks and are sometimes carried in vehicles, though many road cars favor dry-chemical units for versatility.
• Off-road tire inflation: Enthusiasts often carry CO2 “powertanks” to reseat beads and rapidly air up tires after trail runs, where flow rate and portability matter.

These uses are optional or application-specific rather than standard on mass-market passenger cars.

Industry and service uses related to cars

Even when CO2 is not part of a car’s permanent hardware, it is deeply embedded in how vehicles are built, cleaned, and serviced. The following examples are routine in factories and workshops.

• Welding: CO2 (pure or in mixes like C25) is a common shielding gas in MIG/MAG welding for body-in-white assembly and subframes.
• Dry-ice cleaning: Solid CO2 pellets or “snow” gently blast away contaminants from parts, electronics, and paint surfaces without water or secondary waste.
• Leak detection and calibration: CO2 is used as a safe tracer gas for checking HVAC integrity, heat exchangers, and some fuel or EV thermal subsystems.
• Refrigerant service tooling: Workshops servicing R‑744 systems require CO2-rated gauges, hoses, recovery units, and procedures distinct from R‑1234yf.

These activities make CO2 a practical tool throughout the vehicle lifecycle, even if the end customer never sees it.

CO2 in the fuel transition: e-fuels

Captured CO2 is increasingly used as a carbon feedstock to produce synthetic fuels when combined with hydrogen from renewable electricity. These “e-fuels” aim to power existing gasoline or diesel engines with lower net lifecycle emissions, provided the CO2 is from biogenic or direct-air sources and the hydrogen is green. While still niche and relatively costly, pilot production is scaling and may play a role for legacy fleets, motorsport, and hard-to-electrify segments.

What CO2 is not typically used for

Several common misconceptions persist about CO2 in vehicles. The items below clarify where CO2 is generally not part of standard passenger-car systems.

• Airbags: Modern inflators primarily produce nitrogen; CO2 is not the propellant of choice.
• Everyday tire inflation: Standard in-car inflators are air-based; CO2 cartridges are more common for bicycles and off-road accessories, not routine car use.
• Engine operation: CO2 is a combustion byproduct and part of exhaust-gas recirculation flow, but cars do not “use” CO2 as a fuel or combustion aid.

Understanding these boundaries helps distinguish regulated emissions from intentional, engineered uses.

Regulatory and market outlook (2025)

Policy pressure is reshaping thermal management choices. The EU’s tightened F-gas regime (adopted in 2024) further limits high-GWP and PFAS-containing refrigerants across sectors, encouraging natural options like CO2. While R‑1234yf remains dominant in most passenger cars today, R‑744 is gaining traction in buses and select light-duty applications, and interest is rising in EV heat pumps that benefit from CO2’s cold-climate performance. Parallel efforts in e-fuels keep CO2 in focus as a circular carbon feedstock.

Summary

CO2 in cars is more than an emission metric. It is deliberately used as the low-GWP refrigerant R‑744 in some automotive HVAC and heat pumps, sensed in cabins to manage air quality, carried in certain extinguishers and off-road inflation kits, and leveraged throughout manufacturing and service for welding, cleaning, and leak testing. Looking ahead, regulation and electrification are nudging more thermal systems toward CO2, while captured CO2 feeds emerging e-fuels—linking the gas not only to what cars emit, but also to how they cool, are built, and may be powered in the future.