Introduction to Carbon Monoxide (CO)

Carbon Monoxide (CO) is a colorless, odorless, tasteless gas. CO is found in combustion fumes, such as those produced by vehicles, small gasoline engines, stoves, lanterns, charcoal and wood fires, and gas ranges and heating systems. It is a byproduct when there is insufficient oxygen supply to enable complete oxidation to Carbon Dioxide (CO2).

Carbon Monoxide poisoning occurs after enough inhalation of the gas. Known as the “silent killer,” it is undetectable to the human senses, so people may not know that they are being exposed. CO causes adverse effects in humans by combining with hemoglobin to form carboxyhemoglobin in the blood. This prevents hemoglobin from releasing oxygen in tissues, leading to oxygen deprivation within a human body. However, the effects of Carbon Monoxide exposure can vary greatly from person to person depending on age, overall health, and the concentration and length of exposure.

As Carbon Monoxide is considered a toxic gas, it is particularly dangerous in enclosed areas and requires constant monitoring and detection.

Health Hazards

When present in low concentrations through inhalation, Carbon Monoxide poisoning may produce these symptoms:

  • Headache
  • Fatigue
  • Vertigo
  • Vomiting
  • Chest pain
  • Muscle weakness
  • Flu-like symptoms

When present in high concentrations through inhalation, Carbon Monoxide poisoning may produce these symptoms:

  • Unconsciousness
  • Seizure
  • Death

Exposure Limits

When researching CO gas detection solutions, facility managers should be aware of the following CO exposure limits:

Exposure Limits Agency
50 ppm TWA OSHA PEL (General Industry)
50 ppm TWA OSHA PEL (Construction Industry)
50 ppm TWA OSHA PEL (Maritime)
25 ppm TWA ACGIH TLV
35 ppm TWA; 200 ppm Ceiling NIOSH REL
1,200 ppm NIOSH IDLH

Technologies for CO Gas Detection

Electrochemical Sensors

Electrochemical sensors are fuel cell-like devices consisting of an anode, cathode, and electrolyte. The components of the cell are selected so that a subject gas, allowed to diffuse into the cell, will cause a chemical reaction and generate a current. The cells are diffusion-limited, meaning that the rate of the gas entering the cell is solely dependent on the gas concentration. The current generated is proportional to the rate of consumption of the subject gas in the cell.

Learn more about the advantages of using Sierra Monitor's electrochemical gas sensor modules »

Solid State (Semiconductor) Sensors

Solid state (semiconductor) sensors have a resistance that is affected by oxygen adsorbed on the surface of the sensor. Oxygen atoms capture electrons on the semiconductor surface, thereby increasing its resistance. The sensors can be impregnated with dopants such that the sensor's resistance changes when specific gases displace the adsorbed oxygen.

Learn more about the advantages of using Sierra Monitor's solid state gas sensor modules »