Classification Toxic gas, corrosive, powerful disinfectant and bleaching agent
Molecular Formula Cl2
Molecular Weight 70.9 g/mol

Fire Hazard Rating


  • On its own it will not burn, but will support combustion
  • At high temperatures reacts vigorously with most metals and can cause the metal to catch fire or melt

Explosion Range


  • Neither explosive nor flammable on its own
  • Reacts explosively or forms explosive compounds with many common substances such as acetylene, ether, turpentine, ammonia, fuel gas, hydrogen

Liquid Chlorine



Chlorine Gas




  • Transparent, amber coloured, oily fluid
  • Has a high compression ratio (1 L of liquid chlorine expands to form 460 L of pure chlorine gas)


  • Greenish-yellow colour
  • Has a sharp, pungent, penetrating odour
  • It is corrosive and can burn moist body surfaces such as the skin, eyes, nose and respiratory system 
  • It is 2.5 times heavier than air and will pool in low lying areas
  • Is easily liquefied under pressure

Toxic Effects of Chlorine




NOTE: Long-term exposure to chlorine will not help you develop a tolerance to it.






0.03 - 0.1 ppm 
Range of odour threshold

1 - 3 ppm
May cause mild irritation of the eyes, nose, throat

3 - 5 ppm
Stinging or burning of eyes, nose and throat, may cause headache, watering eyes, sneezing, coughing, difficulty breathing, bloody nose and blood-tinged sputum

5 - 15 ppm
Severe irritation of the eyes, nose and respiratory tract

30 - 60 ppm
Immediate difficulty breathing resulting in pulmonary edema (fluid buildup in the lungs), possibly causing suffocation and death

430 ppm
Lethal after 30 minutes

1,000 ppm
Fatal after a few breaths

Exposure Limits of Chlorine





0.5 ppm 
Maximum allowable concentration averaged over an
eight-hour period

1 ppm
Maximum allowable short-term exposure (15 minutes)

10 ppm or more
Immediately dangerous to life and health (IDLH)

Potential Causes of Leaks



  • Valve failure due to impurities lodged in valves
  • Worn, damaged or not using new gaskets
  • Damaged cylinders
  • Corrosion of equipment due to mixture of chlorine gas and moist, humid air
  • Accidental spill or release
  • Using incorrect pressure regulator for cylinder pressure and contents
  • Moving cylinders without ensuring the valve is closed

Chlorine Cylinder Pump Storage Rooms

















NOTE: This is a general guideline. Follow local and appropriate codes/standards/regulations in your area to ensure proper compliance.

  • Access should be restricted to authorized personnel only
  • Posted at the entrance to the room should be a warning sign that chlorine is present
  • Chlorine storage areas should be fire resistant and must be designed so that chlorine containers and equipment are located at the lowest level, sub-surface locations should be avoided
  • Storage rooms with floor areas larger than 19 m2 (rooms approximately 20 ft. x 10 ft.) must have two or more exit doors to ensure accessible escape routes
  • All exit doors must open outwards and must be fitted with panic hardware (a crash bar for easy exit) and not be self-locking
  • Each room or building housing chlorine containers or equipment should have a viewing window at least 30 cm (12 in.) square or larger that will provide a clear view of the container and distribution system
  • All openings in chlorination rooms (for example, in walls or ceilings) must be tightly sealed, including electrical conduits
  • Respiratory protection and protective clothing is required when changing cylinders or handing chlorine compounds
  • If possible cylinder changes should be done when no workers or members of the public are in the building
  • Separate ventilation system inside the room should be on and functional when workers are inside the room
  • All ventilation fans must include switches outside the chlorine room or building, even when an inside switch is installed
  • No other materials, combustible or otherwise, should be stored in the same room as the chlorine cylinders
  • Piping, valves and containers should be closed or capped when not in use to keep out atmospheric moisture such as precipitation or humidity
  • A chlorine gas detection alarm system should be installed with an indicator located outside the room at each entrance
  • Fresh air intakes must be at floor level to provide cross-ventilation using outside air
  • Follow rules for discharging chlorine. During a leak situation the ventilation system must be shut down until confirmed safe to exhaust the gas.






  • Continuous chlorine detection and alarm system for early detection
  • Eye wash and shower facilities
  • First aid kit at each chlorine location
  • Appropriate chlorine repair kits on-site depending on size of container
  • Accessible shutoff valves, pump lockout procedures
  • Automatic shutoff valves triggered by liquid-level gauges
  • Personal protective equipment including an escape respirator
  • All equipment should be protected against mechanical damage
  • Ventilation system and emergency ventilation exhaust system

Emergency Response Planning - steps to address a chlorine leak






  • Provide training, instruction and supervision
  • Write down safe work procedures
  • Understand ventilation systems, dispersion and diluting procedure
  • Initiate product cylinder change disposal, repair, maintenance and recovery/damage control plans
  • Conduct chlorine leak tests during cylinder changes and routine operation of the system
  • Have a diagram with the locations of all cylinder locations and chlorine repair kit locations
  • Have breathing apparatus and protective clothing close by
  • Have emergency and evacuation procedures written down
  • Conduct scheduled emergency drills
  • Have procedure on how to notify emergency response units and adjacent worksites/homes
  • Arrange inspection and maintenance of the chlorine equipment
  • Conduct a formal investigate any time enough chlorine is released to set off the alarm

Chlorine Gas Detection System






  • 24 hour continuous monitoring with an alarm response if chlorine concentrations reach a certain preset level (at or below 0.5 ppm)
  • Tested at least on a monthly basis and calibrated at least annually by qualified personnel
  • Alarm must be able to be heard and seen by all workers, including in the pool area
  • Must have direct readout of the current gas level that can be seen from inside and outside the room (at all entrances)
  • Workers must know the alarm levels and this information must be clearly posted outside the room
  • In most circumstances the alarm should shut down the active ventilation system automatically, but in appropriate circumstances may require the alarm to trigger the ventilation system or exhaust ventilation
  • During routine maintenance a hand held chlorine gas monitor should be used as well

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This document is for informational purposes only. No duty or undertaking is intended or assumed by CETCI.

Every site is different and should develop and implement a health and safety program unique to their own operation.
Always follow local, provincial and federal codes and regulations. If in doubt, contact the appropriate authorities.