CO Concentration as a Design Trigger, Not Just a Number
In an enclosed car park or service tunnel, carbon monoxide (CO) builds quietly whenever engines run. People cannot see it or smell it, and common symptoms look like fatigue or flu.
That is why CO concentration becomes a primary design trigger for ventilation systems. Fans, ducts, and control logic must work together so CO never reaches levels that threaten occupants, maintenance staff, or first responders.
What CO Is and Why It Matters
Carbon monoxide forms when fuel does not burn completely. Petrol and diesel vehicles, small engines, heaters, and some industrial processes all produce it.
CO binds to hemoglobin much more strongly than oxygen. As exposure rises, the blood carries less oxygen, and people develop headaches, confusion, and, at higher levels or longer durations, life-threatening effects.
Unlike many contaminants, CO offers no warning through odor or irritation. That condition makes engineering controls and alarms essential.
Where CO Becomes a Ventilation Issue
Typical high-risk locations
Ventilation design teams watch CO carefully in:
- Enclosed or semi-enclosed car parks
- Vehicle ramps, loading docks, and service tunnels
- Generator rooms and workshops with combustion engines
- Enclosed areas near flue terminations or leaky exhaust systems
In these spaces, natural air exchange often cannot dilute emissions quickly enough, especially during peak traffic or operation.
CO concentration and regulations
Local codes and guidelines set acceptable CO concentration ranges and exposure durations for occupied spaces and egress routes. Many car-park standards define:
- A normal operating level in everyday traffic conditions
- Thresholds where ventilation ramps up
- Alarm points where occupants should leave and operators call emergency services
Ventilation and monitoring systems should align with those defined thresholds rather than informal rules of thumb.
Designing Ventilation to Control CO
Constant versus demand-controlled ventilation
Two broad strategies appear in practice:
- Constant airflow – Fans run continuously at a fixed or staged speed to maintain low CO levels under all expected loads.
- Demand-controlled ventilation – CO sensors modulate fan speed or start additional fans only when concentration increases.
Demand control can reduce energy consumption significantly, but it relies on robust sensing, calibration, and control logic.
Role of CO sensors
CO sensors give the ventilation system a way to “see” contamination in real time. Effective designs consider:
- Placement at representative breathing height, not only near ceilings
- Coverage of zones with higher expected emissions or poor mixing
- Redundancy and regular calibration to avoid drift and blind spots
Control sequences should include different bands: normal, boost ventilation, and alarm, each mapped to clear actions.
Fan and duct arrangements
In enclosed car parks, common approaches include:
- Jet fans that drive air along the ceiling and push CO toward exhaust points
- Ducted supply and exhaust with distributed grilles in deeper layouts
- Mixed systems that use ductwork in some areas and jet fans elsewhere
In each case, the system must sweep stale air through the occupied zone before it leaves, not short-circuit between supply and exhaust near the ceiling.
Operational Practices That Keep CO Under Control
Commissioning and testing
A CO-control system only works if commissioning proves its behavior. Teams should:
- Verify sensor calibration and alarm setpoints
- Test fan staging and VFD responses at simulated CO levels
- Confirm that airflow patterns move air from occupied zones to exhaust points
Test records then support future inspections and audits.
Routine maintenance
Over time, dust, moisture, and mechanical wear can reduce performance. O&M plans should cover:
- Sensor calibration or replacement at manufacturer-recommended intervals
- Fan bearing, belt, and motor checks to keep available capacity reliable
- Verification that jet fans run in the correct direction and achieve expected thrust
- Cleaning of grilles and ducts where buildup could restrict airflow
These tasks maintain both CO control and general AIRFLOW CONTROL performance.
Responding to alarms
Procedures matter as much as hardware. Site instructions should state:
- How staff and occupants must respond when CO alarms sound
- Which areas to evacuate and where to assemble
- Who holds authority to reset systems after an alarm, and under what checks
Clear training ensures that alarms lead to rapid, consistent action.
FAQ
What is a CO-concentration?
A CO concentration describes how much carbon monoxide sits in a volume of air, often measured in parts per million. Higher concentration and longer exposure increase the risk of symptoms and serious health effects.
What causes CO concentration?
CO concentration rises when combustion sources operate in spaces without enough ventilation. Vehicle exhaust, generators, heaters, and some industrial processes release CO, and it accumulates if fresh air does not dilute and remove it effectively.
What concentration of CO is harmful?
Even relatively low levels can cause symptoms over time, and higher levels quickly become dangerous. Exact limits depend on local regulations and exposure duration, but design practice aims to keep CO far below emergency thresholds by using detection and ventilation control.
Where is the greatest CO concentration?
The highest CO concentrations usually occur close to running engines in enclosed or poorly ventilated areas, such as near ramps, congested parking zones, or generator exhausts. Confined spaces with fuel-burning equipment and little fresh air present particular risk.
What level of CO2 in blood is concerning?
CO₂ levels in blood relate to breathing, metabolism, and medical conditions, and doctors evaluate them with arterial blood tests and clinical context. Any concern about blood gases or breathing should go directly to a qualified healthcare professional rather than relying on building ventilation settings.
What should I do if my CO alarm goes off?
Treat a CO alarm as urgent. Move everyone to fresh air, avoid re-entering the area, and contact emergency services or qualified responders. Only trained personnel should investigate the source and reset the alarm after confirming that CO levels have returned to safe values.
Does opening windows reduce CO?
Opening windows can help reduce CO in smaller spaces by increasing natural ventilation, especially if you create cross-flow. In enclosed car parks and large facilities, however, engineered ventilation and exhaust systems remain the primary tools for controlling CO because window openings alone rarely provide predictable, adequate airflow.
About YAOAN VENTILATION
YAOAN VENTILATION delivers optimized air and airflow management solutions backed by nearly three decades of engineering experience. Since 1996, we have focused on industrial-grade ventilation and fire protection systems for commercial buildings, infrastructure, and specialized environments. Our portfolio includes fans, jet fans, dampers, smoke-control components, silencers, and precision-built aluminum ventilation parts designed to integrate with CO monitoring and control strategies in car parks and similar spaces. By combining robust equipment, engineered airflow patterns, and clear control logic, YAOAN VENTILATION helps projects keep CO concentrations within target limits and protect occupants over the full system life.