What is Carbon Monoxide?

Carbon monoxide (CO) is an extremely dangerous gas formed during the combustion of carbon-containing fuels, and can rapidly increase in concentration especially under incomplete combustion conditions. Natural gas, fuel oil, gasoline, LPG, coal and wood can all lead to serious carbon monoxide build-up when used with improperly installed appliances, poorly maintained systems or in inadequately ventilated spaces.

Because it is colourless, odourless and tasteless, and does not cause burning or irritation in the throat when inhaled, it is very difficult for people to notice its presence. For this reason it is often referred to in the literature and public discourse as the “silent killer”, and it represents a critical safety risk in many environments ranging from homes and enclosed car parks to boiler rooms and industrial facilities.

Carbon monoxide exposure can become life-threatening within minutes. Therefore, the use of appropriate combustion technologies, regular maintenance of appliances, properly designed ventilation systems and the commissioning of a reliable CO detection system are all matters of vital importance. The risk level rises especially during the winter months when enclosed spaces are used more intensively, and thus technical measures must be complemented with strong public awareness efforts.

Where is Carbon Monoxide Found?

Carbon monoxide can form in almost any enclosed or semi-enclosed space where carbon-based fuels are used and ventilation is inadequate. The primary high-risk areas can be summarised as follows:

• Enclosed car park areas,
• Mines and underground working spaces,
• Boiler rooms and plant rooms with poor ventilation where carbon-based fuels are used,
• Smoke layers formed in fires together with other toxic gases,
• Underground transport systems and tunnels,
• Enclosed spaces where heaters and equipment operating on propane or LPG are used.

What are the Sources of Carbon Monoxide?

Carbon monoxide is a significant air pollutant both outdoors and indoors. The main sources commonly encountered in everyday life and industrial processes are:

• Vehicle exhaust gases (one of the most important sources in areas with heavy traffic),
• Stoves (especially with incorrect installation, blocked chimneys or poor draft),
• Gas water heaters, combi boilers and boiler systems operating on natural gas/LPG,
• Cigarette smoke,
• Flueless heaters (gas or LPG heater appliances).

In any environment where these sources are present, monitoring combustion quality, performing regular maintenance and using a properly designed carbon monoxide detection system play a critical role in reducing CO risk.

What are the Symptoms of Carbon Monoxide Poisoning?

Symptoms seen in mild carbon monoxide poisoning:

Symptoms that may occur in chronic or more advanced carbon monoxide poisoning:

• Severe headache,
• Marked fatigue and exhaustion,
• Nausea and vomiting,
• Abdominal pain,
• Impairment of cognitive functions (attention, concentration, etc.),
• Feeling dazed, numbness/tingling,
• Blackouts or visual dimming,
• Retinal haemorrhage (fundus bleeding),
• Memory problems,
• Restlessness and behavioural changes,
• Loss of balance and difficulty walking.

In long-term or high-dose exposure, the risk of permanent neurological damage increases; therefore, when such symptoms are observed, medical attention must be sought without delay.

Occupations at High Risk of Carbon Monoxide Exposure

Certain occupational groups are at significantly higher risk of carbon monoxide exposure due to the characteristics of their working environments:

• Traffic police officers,
• Firefighters,
• Staff working in enclosed garages and car parks,
• Workers in the steel and metal industries,
• Personnel involved in paint stripping and solvent-based processes,
• Boiler room and heating plant operators,
• Car mechanics and exhaust service technicians.

Carbon monoxide poisoning is also much more serious in pregnant women, children under two years of age, elderly individuals, people with anaemia and those with respiratory or cardiac disease. In these high-risk groups, severe clinical symptoms may occur even at lower exposure levels.

Stages of Carbon Monoxide Poisoning

First Stage:

A person inhaling CO may initially experience mild drowsiness, lethargy and sleepiness. Concentration decreases and responsiveness to the surroundings weakens. These symptoms indicate the onset of poisoning. At this stage, if the person/people are immediately removed to fresh air, the space is ventilated and professional medical support is sought, the chance of recovery is quite high.

If exposure continues, motor ability decreases noticeably, a feeling of “pleasant drowsiness” sets in and a strong desire to sleep appears. The person usually does not want to leave the environment and has difficulty recognising the danger.

Second Stage:

As poisoning progresses, trembling, muscle contractions, jaw clenching and teeth grinding may be observed. The eyes are often fixed at a single point, consciousness becomes clouded and disturbances in body temperature regulation may occur. This stage indicates that the clinical picture has reached a serious level.

Third and Final Stage:

Breathing and heart rate slow down markedly, body temperature falls and sensation and consciousness are lost. If no intervention is made, this process ends in death. In cases of high-concentration exposure, progression to this stage can occur within a very short time.

The formation of carboxyhaemoglobin, a compound created when carbon monoxide binds to haemoglobin in the blood, may cause a characteristic reddish-pink discolouration of the skin. In some cases, the skin and lips may take on a cherry-red tone and the facial expression may appear as if there is a slight smile. This is an important finding in the medical and forensic assessment of CO poisoning cases.

Carbon Monoxide Detection and Ventilation in Enclosed Car Parks

In enclosed car parks, carbon monoxide (CO) detection and ventilation systems are critical both for protecting human health and for ensuring a safe environment in compliance with regulations. CO released by vehicles at idle or in motion can quickly accumulate in enclosed areas and reach dangerous levels in a short period of time. Therefore, enclosed car park carbon monoxide sensors continuously monitor gas concentration and automatically activate ventilation fans when the predefined threshold values are exceeded. In this way, fresh air circulation is achieved and harmful gases are removed from the environment.

CO detection solutions integrated into modern building automation systems are equipped with features such as staged fan control for energy efficiency, remote monitoring and alarm management, thus supporting both safety and the optimisation of operating costs in enclosed car parks.

Regulatory Definition and Classification of Enclosed Car Parks

Definition in the Turkish Regulation on Fire Protection of Buildings (2009), Article 60:
For enclosed car parks with a total area exceeding 2,000 m², a mechanical smoke extraction system is mandatory. The smoke extraction system must be independent of the systems serving other parts of the building and must provide at least 10 air changes per hour.

Traditional ventilation methods in enclosed car parks:

Simple conventional ventilation systems are commonly used in enclosed car parks. These systems consist of fresh air and exhaust fans; air is circulated directly within the space and exhausted without the use of ductwork.

In conventional ventilation systems, effective air transport is achieved by using ductwork together with fresh air and exhaust fans to continuously supply the space with fresh air and to discharge contaminated air.

In conventional systems, all air is drawn through fans and ducts – this applies both to the supplied fresh air and to the extracted used air. To avoid excessive pressure loss, air velocity is kept as low as possible. However, this implies relatively large duct cross-sections and therefore significant space requirements.

In contrast, jet fan ventilation systems use a completely different approach. In these systems, a small amount of air is drawn into a fan and then discharged at high velocity. The discharged air mass strikes the air in front of the fan, pushing it forward while simultaneously entraining (inducing) the surrounding air. In this way, all of the air in the space is set in motion and transported over distances of 20–40 metres without ductwork. The entire car park effectively acts as an air duct. The principle behind the jet ventilation system is analogous to the principle in rockets, where a small mass of gas (combustion products) is discharged at high speed to produce thrust.

In car park facilities, ventilation fans are used to exhaust both CO and flammable fuel gases. The presence of carbon monoxide in a car park is also an indicator of the presence of other harmful gases (e.g. benzene).

Carbon Monoxide Gas Detection Systems

Even in a well-maintained vehicle just out of service, CO concentration in exhaust gases is around 15,000 ppm; in poorly maintained vehicles this value can reach up to 30,000 ppm. In contrast, the permissible CO limit value in enclosed car parks today is typically around 60 ppm. This comparison clearly demonstrates how serious a risk carbon monoxide poses in an enclosed car park.

The objective is to install a carbon monoxide gas detection system in enclosed car parks and to enable ventilation fans to be automatically controlled based on signals from this system.

In this context, guidance on ventilation and carbon monoxide monitoring and control is often based on the provisions given in the German VDI 2053 guideline, which is one of the most widely applied standards in Europe.

Permissible limit values for CO (carbon monoxide) gas:

As a general reference for all spaces, the following limit values defined by WHO (World Health Organization) are widely used:

Conversion factor at 293 K and 101.3 kPa: 1 ppm = 1.165 mg/m³, 1 mg/m³ = 0.859 ppm

Health risks depending on gas concentration and exposure duration:

• 35 ppm: Maximum limit value allowed by OSHA for an 8-hour work shift; does not cause health problems. WHO considers 10 ppm as the recommended limit.
• 200 ppm: After 2–3 hours of exposure, mild headache, fatigue, nausea, dizziness and feeling dazed occur.
• 400 ppm: After 1–2 hours of exposure, severe headache and intensification of other symptoms; after 3 hours, the situation becomes life-threatening.
• 800 ppm: After 45 minutes of exposure, fatigue, nausea and convulsions; after 2 hours, loss of consciousness; after 3 hours, death.
• 1,600 ppm: Headache, fatigue and nausea within 20 minutes; death within 1 hour.
• 3,200 ppm: Headache, fatigue and nausea after 5–10 minutes; death within 1 hour.
• 6,400 ppm: Headache, fatigue and nausea within 1–2 minutes; death within 5–30 minutes.
• 12,800 ppm: Death within 1–3 minutes.

Permissible and alarm limit values in enclosed car parks:

VDI 2053 treats carbon monoxide (CO) as a reference gas whose control also ensures the removal of many other harmful exhaust gases. Taking into account the reduced CO emission of modern vehicles equipped with catalytic converters, it lowers the previously applied limit value of 100 ppm (15-minute average) to a range of 50–60 ppm.

It also recommends a 120 ppm peak value for the 15-minute average and an instantaneous 250 ppm peak value as alarm thresholds. Accordingly, 100 ppm can be used as the alarm threshold for the first fan speed stage and 200 ppm for the second fan speed stage.

System Components

Carbon Monoxide Detection Systems:

According to VDI 2053, a carbon monoxide monitoring system is defined as a combination of sensing detectors, instruments for monitoring measured and limit values, and series-connected warning and alarm devices.

Typically, the system is a multi-channel structure consisting of CO sensors installed at one or more measuring points. The CO sensors transmit analogue measurement signals to a central monitoring and evaluation control panel, where ventilation and alarm scenarios are triggered according to predefined thresholds.

Carbon Monoxide Detectors:

The guideline does not prescribe a specific sensor measurement principle; however, in order to meet performance criteria such as sensitivity, linearity, measurement uncertainty, zero drift, temperature effects and gas cross-sensitivities, and also based on international practice, electrochemical cell-type sensors are widely accepted as the most reliable sensor technology.

CO Detector Placement Principles

• VDI 2053 specifies that the number of sensors should be determined as a maximum of one sensor per 400 m². In other words, each 400 m² area is defined as one monitoring point.
• Sensors should be installed at a height of approximately 1.5–1.6 m above the floor, corresponding to the average person’s breathing zone.

Warning: Installing CO detectors together with fire detectors at the ceiling is incorrect and significantly reduces detection accuracy.

General Notes for Car Park CO and Fire Systems

• The Turkish Regulation on Fire Protection of Buildings (2009) does not explicitly mandate smoke control in car park ventilation; however, smoke control solutions are often preferred in many projects based on a performance-based design approach.
• In underground car parks, the ceiling height is relatively low (approximately 2.5 m); therefore, in the event of a fire, smoke is expected to spread rapidly over the entire floor. The area around the fire will soon fill with smoke, which will then start to spread to the rest of the car park.

Objectives:

• To extract smoke so that occupants in the car park can escape without being affected by it,
• To control smoke in such a way that firefighters can enter the car park, approach the fire safely and extinguish it.

CMD-500 Carbon Monoxide Panel

System Components

• Single-zone panel,
• Two-zone panel,
• Three-zone panel,
• Expansion module,
• Carbon monoxide detector (ceiling type),
• Carbon monoxide detector (wall type).

System Features

• The system consists of a panel selectable from 1 to 3 zones and detectors connected to the panel via a 2-core cable.
• Maximum cable length up to the last detector is 2 km when using 1.5 mm² cross-section cable.
• All system components are microprocessor-based and detectors use electrochemical sensing cells.
• Up to 32 detectors can be connected per zone.
• Detectors have polarity-free 2-wire connection, enabling monitoring of up to 19,200 m².
• Measurement range is 0–300 ppm.
• Each zone has 3 user-adjustable, threshold-based relay outputs (2 for ventilation, 1 for alarm).

Design and Engineering: Carbon Monoxide Systems

The design and engineering of carbon monoxide systems are critical for ensuring safety in enclosed spaces and for creating an infrastructure compliant with applicable regulations. In this process, a risk analysis is carried out for car parks, boiler rooms, industrial facilities or similar spaces; vehicle intensity, usage scenarios, air circulation patterns, volume size and evacuation routes are all considered to determine the required number and placement of sensors.

CO detectors are designed to work in integration with ventilation fans and building automation systems; staged fan control, alarm management and automatic ventilation strategies are defined according to threshold values. In this way, enclosed car park ventilation and CO control are optimised with respect to both safety and energy efficiency.

During the design phase, relevant standards, local regulations and operational requirements must be considered together, and solutions that support life safety and business continuity while being easy to maintain and sustainable should be preferred.

Carbon Monoxide Detector Placement Principles

• Detector placement should be planned as one detector per 200 m². In other words, each 200 m² area is defined as one monitoring point.
• Sensors should be installed at a height of approximately 1.5–1.6 m from the floor, corresponding to the average human breathing zone.

• Alarm and fault outputs from carbon monoxide panels are monitored via fire detection and alarm systems.
• To enable monitoring via the fire detection and alarm system, 2 monitoring modules (AMD3311) must be added to the project for each carbon monoxide panel.