This page contains abstracts of research on emergency response done by the Transportation of Dangerous Goods Directorate.
On this page
- Chlorine reactivity with environmental materials in atmospheric dispersion models – October 4, 2022
- Evaluating end of life performance and requalification methods for TC 3CCM cylinders – February 15, 2021
- Hypochlorite reactivity – May 19, 2020
- Effectiveness of mercury spill remediation techniques – February 6, 2020
- Contact us
Chlorine reactivity with environmental materials in atmospheric dispersion models – October 4, 2022
In North America, chlorine is one of the most transported gases because it is essential for disinfecting water and sanitizing industrial waste. Scientists suggested that its highly reactive properties with the natural environment and materials could reduce the downwind toxic gas hazards.
It’s hard for computer models to simulate the behaviour of chlorine releases because the gas is heavier than air and reacts strongly with the environment (e.g., soil, plants). It is important to include these reactions in order to predict how a large chlorine cloud would behave. Nevertheless, there were limited understanding of how much plants can react with chlorine gas to better understand how much chlorine can be removed from the air.
This project was a follow-on study after completing the Jack Rabbit II large scale chlorine release program, led by the U.S. Department of Homeland Security’s Science and Technology Directorate Chemical Security Analysis Center. It was partly funded by Defence Research and Development Canada. Transport Canada provided the list of vegetation common in Canada for use in the experiments and provided technical support and direction throughout the project.
The goal of this research was to determine how fast and how much chlorine gas will react when exposed to bare soil and different plants. This could improve the accuracy of computer models that simulate the behaviour of chlorine releases.
During the study, researchers designed and built a chamber to test how the chlorine reacted to soil and different types of plants. We found that reactivity rates vary between plants, and at what point plants stop reducing the amount of chlorine in a gas cloud. This will be used to update computer models that simulate the gas cloud behaviour to limit how much of the gas cloud will react.
- Read the summary report
- To obtain a copy of the report, please visit the U.S. Department of Homeland Security website
- If you have any questions, please email us: TDGScientificResearch-RecherchescientifiqueTMD.TC@tc.gc.ca
Report Title: Chlorine Reactivity with Environmental Materials in Atmospheric Dispersion Models
Authors: Tom Spicer, Shannon B. Fox
Catalogue: CSAC 20-011 (US Department of Homeland Security report number)
Evaluating end of life performance and requalification methods for TC 3CCM cylinders – February 15, 2021
First responders use self-contained breathing equipment so they can breathe in dangerous atmospheres. The compressed air cylinders are usually made of a composite of aluminum and carbon fibre. In Canada, these cylinders expire after 15 years. After that, they must be thrown out and replaced.
In the United States (U.S.), some of these cylinders expire after 30 years. This is allowed, but the cylinders must pass a modal acoustic emission requalification test every five (5) years, once they’ve been in service for 15 years. This decision was based on testing done by the U.S. Department of Transportation.
Transport Canada wanted to do more testing to measure the strength of expired composite cylinders and look at different test methods for requalifying these cylinders.
The department worked with Hexagon Digital Wave, LLC to run more tests, and had two (2) key goals:
- Measure the physical performance of cylinders which had been in service for about 15 years
- Compare results from three (3) different requalification test methods:
- modal acoustic emission
- acoustic emission
We collected used cylinders from fire departments across Canada and put them through tests that are usually performed on new cylinders. This included simulating 15 years of filling cycles in normal, hot, and cold temperatures, and pressurizing cylinders with water until they burst.
We also dropped or damaged some cylinders on purpose before we tested them. In this study, a “false positive” result means that good cylinders are thrown out when they could still be used safely. A “false negative” result means that bad cylinders would continue to be used and could lead to unsafe conditions.
While testing, we did hydrostatic (required by the standard), modal acoustic emission, and acoustic emission testing at the same time. This helped us assess the ability of the test methods to detect damage, and identify which cylinders were still strong enough to pass a burst test.
- The results of requalification by acoustic emission test depended on the acceptance conditions used
- It’s important to note that at the time of publication, acceptance conditions were not yet standardized by any international or Canadian standards organization
- Requalification by modal acoustic emission test used a method from Special Permits issued by the U.S. Department of Transportation and a standard method from ISO
- Hydrostatic testing rejected the fewest cylinders that later passed a burst test. This means that this test had the lowest number of “false positive” results, but it also had the highest number of “false negative” results
- Modal acoustic emission testing passed the fewest cylinders that went on to fail a burst test. This means that this test had the lowest number of “false negative” results
- When it had the same “false negative” rate, acoustic emission test incorrectly rejected many more cylinders than other testing methods. This means that this test had the highest number of “false positive” results
- All the cylinders tested passed the “at time of manufacture” design tests chosen for this study, even though they weren’t new and had already been used for 15 years
- When compared to the stricter burst test requirement for new cylinders, most of the cylinders we tested met the strength requirement
To get a copy of the report, please contact us.
Catalogue Number: T86-66/2020E-PDF
Hypochlorites reactivity – May 19, 2020
Hypochlorites are found in many common cleaning products, such as bleach and swimming pool water treatment products. They are generally stable, but they can be harmful to your health if you don’t use them correctly. If you mix them with other cleaning products, or expose them to small amounts of water, they may release toxic chlorine gas.
Transport Canada studied how some hypochlorite products react based on factors like temperature and mixing speed. To test for potential chlorine release from liquid hypochlorites, we conducted experiments where a strong acid, hydrochloric acid (HCl), was slowly added to different liquid hypochlorites until chlorine gas was produced. To test solid hypochlorite products, we added small amounts of water and monitored for any gas produced or temperature change over a period of time.
The liquid hypochlorite study found:
- the reaction starts fast, releasing chlorine gas very soon after the acid is added
- the amount of chlorine gas produced from the reaction was toxic for humans if allowed to accumulate in a closed space with no ventilation
- if the hypochlorite is not mixed thoroughly with a strong acid, the reaction can continue releasing chlorine gas up to 2 hours after they are combined based on the products tested
- as the temperature increases, the reaction occurs faster releasing chlorine gas at a faster rate
The solid hypochlorite study found:
- the reaction between solid hypochlorites and water produced little to no chlorine gas
- mixing the solid hypochlorite product in water did not create any significant amount of gas, even at different temperatures and mixing speeds
- the reaction releases heat and oxygen, which can increase the risk of a fire near an ignition source
The Canadian Transport Emergency Centre (CANUTEC) used these results to develop questions to ask the public during a hypochlorite incident, and aid first responders in predicting potential chlorine release. CANUTEC also used these results to develop recommendations for many situations involving solid and liquid hypochlorites. You should consult CANUTEC for incidents that may involve hypochlorites.
To get a copy of the report, please contact us.
Catalogue Number: T86-63/2020E-PDF
Effectiveness of mercury spill remediation techniques – February 6, 2020
Common products like thermometers and fluorescent lights can cause mercury spills when broken. After mercury is spilled, it evaporates and forms toxic vapours which can cause long-term health problems. Two treatments taken from the literature suggested to clean mercury spills by:
- physical removal of mercury beads, then covering the spill with sulfur powder
- physical removal of mercury beads, then wiping the spill with vinegar followed by hydrogen peroxide in concentrations available to the public
The study investigated how effective these treatments are at limiting mercury vapour formation.
For each treatment, the concentration of mercury vapours was analyzed using two methods; the first method took measurements at set intervals, while the second method measured continuously. Gravimetric analysis is a common technique for measuring masses in mixtures and was used to analyze the unreacted mercury after each treatment.
The study compared the concentration of mercury vapours to the baseline vapour pressure of mercury. The study also explored the effect of stirring on the reaction rate for each treatment. The key takeaways are:
- For mercury that isn’t treated, the maximum amount of vapours in a closed environment is reached in a few hours. At peak concentration, the levels of mercury vapour is outside of the safe limits for human exposure. When mercury is stirred on its own with no treatment, the vapour gets to its maximum concentration within an hour.
- When the mercury is treated with sulphur powder, the concentration of mercury vapour is lowered. However, the amount is still higher than safe limits. The reaction is also very slow, which can take several months to finish.
- When the mercury is treated with vinegar and hydrogen peroxide, the concentration of mercury vapour is also lowered, but remains higher than what is considered safe. The reaction is slow and creates mercury acetate, which is hazardous by skin contact. This mixture also releases oxygen, which can pose a risk in the case of a fire.
Overall, the study shows that the sulphur and vinegar-hydrogen peroxide treatments are ineffective at reducing mercury vapours in the air to safe levels in a reasonable amount of time.
Based on the findings, the Canadian Transport Emergency Centre (CANUTEC) recommends physical removal of mercury beads and ventilation of the affected area for cleaning small, uncomplicated, mercury spills. For larger spills or in case of doubt, professionals such as CANUTEC should be consulted.
To get a copy of the report, please contact us.
Catalogue Number: T86-60/2020E-PDF
Safety Research and Analysis Branch
Transportation of Dangerous Goods Directorate