When something smells gassy

Whether it is toxic or flammable, a gas leak can be devasting. Fortunately, the right gas-detection technology can minimise harm to employees and the environment

Black smoke bellowed into the air for almost four days in March 2019, following a petrochemical fire in Deer Park, which is 32 km from Houston in the United States (US). The fire that caused the closure of schools, roads and a shipping channel was attributed to a lack of gas-detection and alert systems according to the US Chemical Safety and Hazard Investigation Board report.

According to the investigation, the flammable gas butane was transferred into one of the tanks that contained naphtha, a flammable liquid used as feedstock in gasoline production. However, a mechanical problem developed during the mixing process, and the naphtha began to leak out of the tank. Employees were unaware of this and no alarms were activated because a gas-detection system had not been fitted.

An estimated three hours passed between the initial leak and when the fire broke out – plenty of time to address the situation if employees had been aware of the leak. The fire then spread to other nearby tanks. Fortunately, no one was injured during the fire. It did, however, highlight the importance of implementing detection and alarm systems when working with petrochemicals.

Fixed gas detectors

In areas where gas is used or stored, it is important to install fixed gas detectors, which will provide around the clock monitoring and alert employees to any potential toxic gas leaks, the risk of asphyxiation and the potential risk of an explosion.

As each detector is unique, it is important to have a qualified installation engineer conduct a site survey to determine the type of gas detector required, where it should be placed and the ideal type of alarm system. The location is important as each gas behaves differently.

When gases are heavier than ambient air (for example, nitric oxide and hydrogen sulphide), detectors should be placed as close as possible to the height at which personnel will be exposed. This might mean placing the device at breathing height, which is usually around 1,5 to 1,8 m. As carbon dioxide will sink to floor level, in this instance detectors should be closer to the ground.

The ideal location for a detector will also be determined by environmental factors, including temperature or air flow. It might be necessary, for example, to ensure the detector is placed down-wind from the potential leak source.

While essential, fixed systems do pose some limitations. If the gas is beyond the reach of the detector, it can still pose a very serious health and safety risk. Portable gas detectors can further ensure the safety of employees.

Portable gas detectors

Mobile or portable gas detectors are worn on a person and assist in alerting the wearer when gas levels are harmful. This is particularly useful in areas where it is not possible to place a fixed gas detector.

The speed and accuracy of the portable gas detector’s reading is vital to ensure the safety of the worker. These detectors also need to be simple for the worker to use and understand. As portable gas detectors can test for one or more gases, it is important to first establish the risks or hazardous gases to which employees might be exposed.

To support the gas detectors, companies can also utilise software or management tools to ensure the equipment remains calibrated. Some software allows portable gas detectors to send notifications to a control room or third-party device if its alarm goes off and the employee fails to respond. This can be useful if the employee collapses, for example.

Additional protection

In addition to ensuring there are an adequate number of efficient gas detectors to monitor any potential leaks, the petrochemical industry can also provide training to ensure employees are adequately prepared to respond to leaks. While most of the workforce will be somewhat, if not
very, informed, there is value in providing refresher courses regarding the hazards of the gases found in the workplace.

Besides training employees on how to respond to gas leaks, it is important to undertake regular drills to ensure that efficient evacuations take place when needed. Strict maintenance and inspection protocol should be enforced in areas where gas is stored, as well as on detection systems to ensure these are effective.

Employers can provide additional protective clothing to employees who are frequently in an area where a hazardous gas is present or there is a risk of its presence. Respiratory devices can also be particularly useful.

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