If you have been around an ozone system for any length of time, you have experienced the elusive ozone leak. Ozone leaks can be frustrating. Ozone leaks can make for a bad day. Ozone leaks can even bring an end to what would otherwise be a successful ozone project. This document is intended to provide some tips and advice on how to find those elusive ozone leaks.
Ozone piping and delivery systems used in continuous duty will eventually leak. It is a fact of life that cannot be ignored. The question is when, not if, the piping and fittings carrying ozone gas will leak. Understanding that leaks will happen is an important step to operating an ozone system for any long term application.
Ozone is regulated by OSHA as a gas that is potentially dangerous to human life. The specifics of these regulations are covered in other articles, however here are the basics:
- 0.3 ppm for no more than 15 minutes of exposure
- 0.1 ppm for 8 hours per day of exposure doing light work
- 0.08 ppm for 8 hours per day of exposure doing moderate work
For more information on OSHA regulations of ozone see this web page: http://www.osha.gov/dts/chemicalsampling/data/CH_259300.html
Why are Ozone Leaks so Hard to Find?
Ozone has a short half life. This means ozone will naturally break down into oxygen very quickly. In a normal room, at standard operating conditions, the half life of ozone averages 20-30 minutes. This may make it hard to find ozone leaks, especially if the leak is intermittent.
Ozone has a low vapor pressure, and therefore does not fill the room uniformly. If you could see ozone in a room it would look similar to smoke from a cigarette wafting carelessly through the room on its own terms. This may make unusually high ozone levels detectable in areas far from where the ozone is actually escaping.
Ozone tends to cling to rough surfaces such as fabrics. You will notice that long after ozone levels have been depleted in the area, your arms and shirt may still carry an ozone odor. This same phenomenon may occur near walls, carpet and other surfaces.
Small ozone leaks can cause very high ambient ozone levels. Ozone gas at 10% by weight equals 68,800 ppm. Even in a large room with good ventilation, it is easy to see how an ozone level above 0.1 ppm is achievable. Also, consider this example: 10% ozone gas leaking into a utility room 10' x 10' x 10' (1000 cubic feet) at a flow rate of 0.01 lpm flow rate could achieve a 1.3 ppm ambient ozone level based on a typical ozone gas half life of 20 minutes. This is an extreme example; however, it is worth considering that it will be extremely difficult to find a leak as small as 0.01 lpm, yet it may cause unsafe ozone levels in your application. Consider your application and consider how small of an ozone leak could create ozone levels above the OSHA threshold of 0.1 ppm. You may be looking for a smaller leak than you think ...
Where to Look for Ozone Leaks
Ozone gas will leak from any tubing, piping or fitting that is carrying ozone gas. Any material used that is not ozone resistant (Ozone Compatible Materials) is most likely to be the cause of the leak. These parts should be replaced. Ozone systems should always use all ozone resistant materials for plumbing ozone gas. Below is a list of common areas that leak ozone:
- All Fittings and Connections - Threaded fittings are common leak points, as well as compression fittings using different material tubing and/or fittings (example: Teflon tubing in stainless steel compression fitting).
- Tubing or piping that may be rubbing against something.
- Valves or any moving part. Ball valves commonly leak from the handle area and needle valves commonly leak from the shaft.
- Ozone generator corona cell.
- Flow meters can leak on tube seals and body.
Basically, anywhere ozone gas is plumbed. While ozone will typically not leak from long runs of teflon or stainless steel tubing, rule nothing out. Start your search in the obvious places and throw out and replace any non ozone resistant materials.
Tips on Finding Ozone Leaks
Enough bad news, how do we find these elusive ozone leaks if and when they occur? That is the question we are asked almost every day. We have some great tips and suggestions below.
Remember, when looking for ozone leaks, you may have a short window of time before the ozone level you are exposed to rises above safe levels. Keep an ozone sensor with you or leave the integrated ozone sensor in tact. When the ozone level is too high; get out, take a break and come back in 20-30 minutes.
Below are some methods we use and the pros and cons of each.
This is an obvious answer. Use an Ozone Sensor and let it do the work for you. If it were only that easy ...
Many ozone sensors do not respond to ozone immediately and have a delay, that simply will not work to find an ozone leak in real time. An ozone sensor that responds to ozone immediately is absolutely necessary. Also, some ozone sensors will require a warm-up period. Ensure your ozone monitor is warmed up and ready to detect ozone. Below you will find a few examples of ozone sensors that do work. These are by no means the only sensors available that could be used, they are just our recommendations.
The favorite ozone monitor for leak detection is the C16 from Analytical Technologies Inc. (ATI).
The C-16 has a long probe with a sample pump. The sample pump pulls ozone gas to the internal sensor in real time. This allows you to get anywhere and really pinpoint the exact leak location. The C-16 has a durable carry case.
When using this sensor or any others; place it directly against the piping or fittings in question and move it SLOWLY along the piping until the reading goes up. Take your time and ensure that you have pinpointed the location, remember air flow may be causing an ozone leak from another location to fool you, make sure you rule this out. After you are certain you have found the leak, keep in mind this may still be the general location. Ozone is tricky that way, it tends to trick you and your ozone sensor. Visually inspect all tubing and fittings, attempt to repair the leak if it is an easy fix. If you are not certain you found the specific fitting you may have to revert to the soapy water trick (see below) to pinpoint the leak.
Soap and Water
The old soap and water trick is still a favorite method of finding ozone leaks. After years in this business and countless elusive ozone leaks, a spray bottle and dish soap is still a great help. Why is this so great you ask?
- No special tools, you can get a spray bottle and dish soap at every department store, grocery store, etc in the world.
- You can turn the ozone generator OFF! Now you are looking for an oxygen or air leak. No more safety concerns.
- This method works, it just plain works.
For this method you need any old spray bottle and some dish soap. Don't get too picky on ratios or mixing, put a copious amount of dish soap in the bottom of your spray bottle and fill the rest with water. Shake well and get to work.
Spray ALL the piping and fittings with generous amounts of your newly created concoction. Then, sit back and wait for the bubbles. Leaks may show up right away or it might take up to a minute to show very small leaks. This method will find the smallest of leaks. Tiny bubbles are created around small leaks and larger leaks will create large bubbles.
This method will not find the largest of leaks. Large leaks will blow the water away and never create bubbles. If the leak is this large you may be able to hear it, feel it or find it with an ozone sensor.
This method will not work well on large piping (larger than 1/2" OD). There is too much surface area to create bubbles from the leak. For those scenarios it is best to use an ozone sensor or potassium iodide.
Chemical Detection (Potassium Iodide)
A potassium iodide solution (2% KI) can be soaked on a white rag for chemical detection. In the presence of ozone the rag will turn brownish or red due to oxidation by ozone gas. This is a good method to pinpoint ozone leaks in large ozone gas piping, tubing and fittings when soapy water will not be effective. This method will require some method of finding the general area of the ozone leak. An ozone sensor should be used to find the general area of the potential leak, then the chemical potassium iodide soaked rag can be laid over this connection to determine exactly what area of the rag changes color. This will pinpoint exactly where the leaky fitting is located.
Your nose is NOT an ozone sensor or an ozone leak detector! So don't use it, or trust it. If you have an ozone leak that you detected with your nose, good for you. Now, go get an ozone sensor and verify the ozone level, then get the proper tools and go find that ozone leak.
Hopefully this helps you. Whenever troubleshooting any system a little common sense and patience will go a long ways. Take your time, take a break if you need to and find that leak. But when you do find that leak make sure you replace that faulty tubing, fitting, valve, etc so it does not happen again.