Is Gas Detection Required for Outdoor Storage of Chlorine Cylinders and Containers?

Chlorine is an essential chemical in any industrialized society. Widely used as a disinfectant to kill bacteria, treat drinking water, and maintain proper swimming pool chemistry, chlorine is also acutely toxic, with low levels of exposure causing nose, throat, and eye irritation. High levels of chlorine exposure can result in permanent respiratory or eye damage, and possibly worse.


Anhydrous chlorine (as opposed to chlorine/water solutions) is typically transported and stored as a liquefied gas within cylinders or ton containers. When stored or used indoors it is essential that gas detection and ventilation be available to prevent dangerous concentrations from collecting.

Often, however, chlorine cylinders and containers are stored outdoors. Is gas detection required in this case?

The Chlorine Institute is a wealth of resources for all things chlorine. Many of the pamphlets they have published can be download free of cost. Section 4.4.3 in Pamphlet 155 requires that “Installations, manned or unmanned, where chlorine is stored or used should have gas detection equipment to monitor for chlorine releases“.


Since this section does not differentiate between indoor and outdoor use, we reached out to The Chlorine Institute to clarify the issue.

Their response removed all ambiguity:

“That section does not specify that the monitors would only be needed for indoor storage, so it’s safe to assume that the recommendations for gas detection equipment are for outdoor storage as well. There are some general recommendations for air monitoring in Pamphlet 73: Atmospheric Monitoring Equipment for Chlorine, which may be helpful for you.”

In short, gas detection is required regardless of chlorine being stored indoors or outdoors.

Pamphlet 73 is also available at no cost online. We suggest chlorine operators add these documents to their library and verify that gas detection will satisfy regulatory expectations.

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