Introduction to Chlorine (Cl2)

Chlorine (Cl2) is a naturally occurring, highly reactive gas found in various industrial settings where it used for production and disinfection. It is 2.5 times as heavy as air and has an intensely disagreeable suffocating odor. Infamously used during World War I as a choking (pulmonary) agent, Chlorine gas is very poisonous when exposed through skin and eye contact and inhalation. It has a yellow-green color, and a pungent, irritating odor similar to that of bleach.

Chlorine is a highly used chemical in industry and society. Exposures to toxic levels of Chlorine gas are generally accidental. If not detected properly, Chlorine poisoning can cause different symptoms throughout the human body. It is therefore imperative to monitor Cl2 levels with gas sensors anywhere that Chlorine is used or produced.

Health Hazards

When present in low concentrations, Chlorine gas may produce these symptoms:

  • Eye, nose, throat, respiratory irritation
  • Excess salivation
  • Excitement and restlessness

When present in high concentrations, Chlorine gas may produce these symptoms:

  • Blurred vision
  • Nausea
  • Vomiting
  • Headache
  • Dyspnea
  • Chest pain
  • Muscle weakness
  • Esophageal perforation

Exposure Limits

When researching Cl2 gas detection solutions, facility managers should be aware of the following Cl2 exposure limits:

Exposure LimitsAgency
1 ppm (ceiling)OSHA PEL (General Industry)
1 ppm TWAOSHA PEL (Maritime)
0.5 ppm TWA, 1.0 ppm STELACGIH TLV
0.5 ppm TWA, 1.0 ppm STELNIOSH REL

Technology for Cl2 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.

Advantages to using an electrochemical sensor include allowing sensors to be specific to a particular gas in the parts-per-million range, low power requirements, high accuracy, and lower cost than other gas detection technologies. However, electrochemical sensors are sensitive to temperature, subject to interference from other gases, and have a shorter lifespan the greater the exposure is to the targeted gas.

Sierra Monitor electrochemical sensors provide improved reliability by allowing the gas to diffuse into the sensor through a capillary port, rather than diffusing through membranes. The result is an extremely stable sensor with very low temperature and pressure coefficients, and the capability to monitor gas as a percent by volume (oxygen) and ppm (toxics).