Ozone leak sends three to the hospital

An Arizona water treatment plant that uses ozone for water treatment had a minor equipment failure that sent three people to the hospital. The plant was evacuated and the fire department Haz-Mat team was called to the scene.  Read full story below:


GILBERT, AZ – A water treatment plant in Gilbert was evacuated Friday because of a hazardous materials situation on Friday.

Jennifer Alvarez, digital media and marketing officer for Gilbert, said in am email to ABC15 that a “minor equipment failure” resulted in “a small release of ozone” at the plant.

Up to thirty people were in the area at the time, a spokesman for Gilbert Fire Department said.

Three people were transported to the hospital, said Alvarez. The other people were treated on-site.

The plant has since been given the all-clear, she said, and emplyees have returned to work.

The SanTan Vista Drinking Water Treatment Plant is located near Ocotillo and Recker roads. According to the Town of Gilbert, the treatment plant receives water from Central Arizona Project’s Colorado River watershed through a 14-mile ductile iron pipeline.

The plant treats 24 million gallons of water a day, which is split evenly between Gilbert and Chandler, the website said.

The plant is undergoing an expansion project that began in 2016 and is slated to be completed in 2018.

Ozone is commonly used for water treatment.  The use of ozone in water treatment and many applications is perfectly safe, and in fact safer than alternative chemicals like Chlorine.  It should be simple to maintain a safe environment around your ozone equipment.

Ozone Leaks and ambient ozone levels are not issues to be taken lightly by your safety team.  Ensure you have ozone monitors on-site, ensure they are working, and ensure your staff knows how to keep themselves safe in your facility.  Need help with ozone equipment maintenance, ozone sensors, and ozone safety?  Contact our office, we would be glad to help.

Need an ozone monitor?  Click HERE to view our complete line of ozone safety monitors.

Ozone Safety Updated from OSHA

There have recently been some safety regulation updates from OSHA when it comes to Ozone.  Below is the information on the old guidelines, new guidelines, and information on being compliant with the new guidelines.



The old OSHA guidelines were based on the permissible level of exposure to a specific amount of ozone based on different intervals of time and the type of work (example: 0.08 ppm for 8 hours per day exposure doing moderate work, and 0.05ppm for 8 hours per day exposure doing heavy work), however, this is not the case anymore.



The current OSHA Permissible Exposure Limit (PEL) for an 8 hour work day (of a 40 hour work week), is 0.1 ppm time weighted average (TWA) of ozone.

It’s our understanding that in order to be in compliance with the new OSHA regulations (see 29 CFR 1910.1000), implementation of something (monitor or control device) to ensure ozone exposure to employees does not exceed the 0.1ppm TWA during the 8 hour work shift.


Below is the calculation that can be used for the cumulative exposure for the 8 hour work shift:

(Ca Ta+Cb Tb+. . .Cn Tn)÷8 = E
E is the equivalent exposure for the working shift. (Ozone = 0.1 ppm)
C is the concentration during any period of time (T) where the concentration remains constant.
T is the duration in hours of the exposure at the concentration C.

For example
([0.5ppm x 1 hour] + [0.02 x 2 hours] + [0.052ppm x 5 hours]) ÷ 8 = 0.1 ppm

Ozone levels can be higher than the 0.1ppm standard for a short period of time as long as low levels at other times of the day still equal out to 0.1ppm of ozone over the 8 hour shift.

For example (0.1 all day):
(0.1ppm x 8 hour) ÷ 8 = 0.1

When using this calculation the value of E should never exceed 0.1 ppm of ozone in an 8 hour work shift.



If monitoring equipment is not in place, then protective equipment or other means must be taken to ensure that the permissible exposure limit of 0.1 ppm ozone TWA in an 8 hour work day is meet.  Another OSHA standard is any workers exposed to ozone have the right to know that they are exposed to ozone and the given exposure amount, and informed of the hazards/risks of ozone, as well as given protective measures.

In order to ensure being compliant, we would recommend use of a Ozone Monitoring/Detection Device that is connected to an alarm that triggers when ozone levels exceed the 0.1 ppm limit.  That way you can monitor the length of time ozone levels are above the permissible limits and use the calculation give above to ensure the time weighted average does not exceed 0.1 ppm.

Ozone Monitors that are offered by Oxidation Technologies
Ozone Monitors that are offered by Oxidation Technologies

For more information on ozone safety can be found on our website.