CO₂ vs O₂ Monitoring
What’s the Difference Between CO₂ and O₂ Monitoring?
Carbon dioxide (CO₂) and oxygen (O₂) sensors monitor completely different atmospheric risks.
CO₂ sensors measure carbon dioxide concentration, which becomes toxic at elevated levels. Oxygen sensors measure the percentage of oxygen in the air, identifying oxygen depletion or oxygen enrichment hazards.
Using the wrong type of sensor can allow dangerous conditions to go undetected.
Why This Matters
CO₂ and O₂ monitoring are often confused, particularly in environments where multiple gases are present.
A common misconception is that an oxygen monitor can detect a CO₂ leak. This is incorrect.
CO₂ can reach dangerous, and potentially fatal, concentrations long before oxygen levels drop enough to trigger an O₂ alarm. Relying on the wrong type of monitor can result in delayed warnings and serious safety risks.
What Is CO₂ Monitoring?
Carbon dioxide monitoring measures the concentration of CO₂ gas in the air.
CO₂ is:
- Colorless and odorless
- Naturally present at low levels (~0.04%)
- Hazardous at elevated concentrations
CO₂ monitoring is used to detect:
- Gas leaks
- Gas buildup in enclosed spaces
- Poor ventilation
At higher concentrations, CO₂ can cause:
- Dizziness
- Headaches
- Confusion
- Loss of consciousness
What Is O₂ Monitoring?
Oxygen monitoring measures the percentage of oxygen present in the air.
Normal atmospheric oxygen levels are approximately 20.9%.
O₂ monitoring is used to detect:
- Oxygen depletion (low oxygen levels)
- Oxygen enrichment (increased fire risk)
Oxygen depletion is often caused by gases such as:
- Carbon monoxide (CO)
- Carbon dioxide (CO₂)
- Nitrogen (N₂)
Low oxygen levels, known as hypoxemia, can lead to:
- Impaired judgment
- Loss of consciousness
- Asphyxiation
CO₂ vs O₂ monitoring: key differences
| Feature | Specification |
|---|---|
| Input Voltage Range | 18 to 36 V DC |
| Power consumption | 150 mW The power supply inputs are galvanically isolated from the outputs. This will allow the analogue outputs to float with respect to system ground, to avoid earth loops |
| Pressure range | 0 to 60 bara |
| Storage temperature | 0 to 100% RH |
| Weight | 89g / 3.1oz |
| Enclosure material | Aluminium sensor enclosure - Anodised black Amphenol MIL-DTL-38999 Series III connector - nickel coated aluminium |
Can an Oxygen Monitor Detect CO₂ Leaks?
No.
An oxygen monitor does not measure carbon dioxide levels.
During a CO₂ leak:
CO₂ concentrations can rise rapidly
Oxygen levels decrease much more slowly
By the time oxygen levels fall enough to trigger an O₂ alarm, typically around 19.5%, CO₂ concentrations may already be dangerously high.
This is why a dedicated CO₂ monitor is essential anywhere carbon dioxide is used or stored.
When Do You Need a CO₂ Monitor?
You need a CO₂ monitor in environments where carbon dioxide is:
- Stored (gas cylinders, bar cellars)
- Produced (fermentation processes)
Used in industrial or commercial processes such as:
- Drink carbonation
- Food packaging
- Welding
- Medical procedures
When Do You Need an O₂ Monitor?
Oxygen monitoring is required in environments where other gases may displace oxygen in the air, creating a risk of oxygen depletion.
Common Applications for CO₂ Monitoring
- Breweries and beverage production
- Restaurants and cellar environments
- Laboratories and medical facilities
- Indoor agriculture and growing environments
Common Applications for O₂ Monitoring
- Nitrogen storage areas
- Confined spaces, including cellars and armored vehicles
- Industrial gas storage environments
- Laboratories
When Do You Need Both CO₂ and O₂ Monitoring?
In many environments, both carbon dioxide and oxygen can present safety risks.
Examples include:
- Breweries (CO₂ and nitrogen)
- Laboratories using multiple gases
- Food production facilities
In these environments, a dual gas monitoring solution is recommended to ensure complete atmospheric protection.
Where Should Sensors Be Installed?
CO₂ Sensors
- Low to the ground, as CO₂ is denser than air
- Near potential leak sources
O₂ Sensors
- At breathing height
- In areas where gas displacement may occur
Correct sensor placement is essential to ensure reliable and accurate gas detection.
Common Safety Mistakes
Some of the most common safety issues include:
- Using an oxygen monitor to detect CO₂
- Assuming CO₂ can be detected by smell
- Installing sensors in the wrong location
- Failing to properly monitor multi-gas environments
These mistakes can lead to delayed detection and increased safety risks.
Recommended Monitoring Approach
To ensure reliable safety, it is essential to select the correct sensor for the environment and the gases involved. You should:
- Use CO₂ monitors for carbon dioxide hazards
- Use O₂ monitors for oxygen depletion risks
- Use dual-gas monitoring where multiple gases are present
CO₂ Calculator
Many people believe an oxygen (O₂) monitor alone is enough to stay safe when using carbon dioxide (CO₂). In reality, CO₂ is a toxic gas, and dangerous concentrations can be reached long before an O₂ alarm activates.
As CO₂ leaks into an area, it displaces oxygen. However, most O₂ monitors only trigger alarms at around 19.5% O₂, by which point CO₂ levels may already be hazardous.
If your facility uses CO₂, a dedicated CO₂ monitor is essential. It provides earlier warning of leaks, helping protect personnel, reduce product loss, and minimize costly CO₂ waste.
Use this calculator to see how increasing CO₂ concentrations affect surrounding oxygen levels.
SLOT Specified level of toxicity (1 - 5% of fatalities) SLOD Significant likelihood of death (50% fatalities)
Learn more about our CO₂ monitoring solutions or explore our O₂ gas detection systems to find the right protection for your application.
FAQs
Can CO₂ be detected by smell?
No. Carbon dioxide is colorless and odorless.
What happens if CO₂ levels increase?
Raised CO₂ levels can cause dizziness, confusion, and loss of consciousness.
What is a safe oxygen level?
Normal oxygen levels are around 20.9%. Oxygen levels below 19.5% are considered unsafe.
Can one monitor detect both CO₂ and O₂?
Only if it is specifically designed as a dual-gas monitor and includes both CO₂ and O₂ sensors.
Key takeaway
CO₂ and O₂ monitoring address different atmospheric hazards and are not interchangeable.
Using the correct type of gas monitor, or a combination of both, is essential to maintain safe environments and protect against potentially life-threatening conditions.