Asked.
And Answered.
Frequently Asked Questions
Carbon monoxide (CO) and nitrogen dioxide (NO₂) monitoring systems are life-safety systems governed by mechanical, fire and occupational safety codes. Here are some straightforward answers to common questions we hear from owners, engineers and facility teams. The information here is intended as general guidance to help you understand typical system requirements, best practices and considerations.
Because gas monitoring regulations can differ by jurisdiction, building type and authority having jurisdiction (AHJ), specific requirements should always be confirmed locally. ACES works within these frameworks every day and can help interpret how applicable codes apply to your facility and project.
What is carbon monoxide (CO)?
Carbon monoxide (CO) is a toxic gas produced when carbon-based fuels such as gasoline, natural gas, diesel, oil, propane, wood or coal do not fully combust. Because CO has no color, odor or taste, people can be exposed without warning.
- Colorless, odorless, poisonous gas
- Produced by incomplete combustion
- Common in vehicle exhaust and fuel-burning equipment
Why is carbon monoxide dangerous?
When inhaled, CO binds to hemoglobin with over 200 times the affinity of oxygen, preventing oxygen from reaching vital organs. Symptoms range from headaches and dizziness to loss of consciousness and death.
- Prevents oxygen delivery in the body
- Causes symptoms before detection
- Can be fatal at high concentrations
What is nitrogen dioxide (NO₂)?
Nitrogen dioxide is produced by fossil fuel combustion and is especially prevalent in enclosed garages and industrial spaces. Long-term exposure increases the risk of chronic respiratory conditions.
- Harmful combustion byproduct
- Common in vehicle exhaust
- Serious respiratory irritant
What should I do if a sensor alarms or faults?
Verify basic system status and contact a gas monitoring specialist promptly to ensure continued protection and compliance.
Check the displayed gas level and confirm exhaust fans and ventilation systems are operating.
Limit exposure in the affected area by keeping people clear until readings return to normal.
Monitor conditions to verify gas levels are stabilizing or decreasing.
If levels continue to rise or do not decrease, follow site emergency procedures and contact local emergency services as appropriate, then arrange for system inspection.
Compliance
Code requirements
Most jurisdictions require CO monitoring under the International Mechanical Code and related standards. Local fire departments may inspect systems and request maintenance documentation.
- Required in most enclosed garages
- Referenced by IMC, OSHA, NIOSH, NFPA
Sensor calibration
Electrochemical sensors degrade over time and must be periodically tested and calibrated to remain accurate and compliant. Annual calibration is typical, though conditions may require more frequent service.
- Regular calibration required
- Frequency varies by manufacturer
System maintenance
Unmaintained systems may drift out of calibration or fail, leading to unsafe conditions, failed inspections and possible fines.
- Increased safety risk
- Higher energy costs
- Potential code violations