GAS DETECTION & MONITORING
FAIL TO PREPARE, PREPARE TO FAIL
Gary Collins, Regional Director for portables at Scott Safety, discusses the importance of safety critical pre-planning work and rigorous testing of gas detection equipment when working in confined spaces.
Around 15 workers die every year as a result of entering a confined space and many more are seriously injured according to HSE. A tragic 60% of those who die are workers who had attempted to rescue those already trapped.
With these statistics in mind a confined space is no place to learn on the go, so it is vital that both employers and workers have a greater understanding of the risks associated with an individual site, particularly the presence of toxic gases.
WHAT IS A CONFINED SPACE? Defined by the HSE as a place which is substantially enclosed (though not always entirely), and where serious injury can occur from hazardous substances or conditions within the space or nearby (e.g. lack of oxygen), confined spaces can be life- threatening if you don’t know what you’re dealing with.
Toxic gases can build up in many ways, compromising the quality of the air within a confined space. Some examples include sewers and manholes and in pits connected to the system, entry into tanks or vessels from connecting pipework, or leaks into trenches and pits in contaminated land, such as old refuse tips and gas works. Many toxic gases are
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dangerous in very low concentrations. In some cases a concentration of only a few parts per million can quickly become lethal.
The Management of Health and Safety at Work Regulations 1999 clearly state that employers must ensure that a suitable and sufficient risk assessment is conducted before work commences. The Confined Spaces Regulations 1997 takes this a step further, stating “so far as is reasonably practicable, no person at work shall enter or carry out any work in or (other than as a result of an emergency) leave a confined space otherwise than in accordance with a system of work which, in relation to any relevant specified risks, renders that work safe and without risks to health.” However, sadly this is not always the reality, and in many cases of serious injury and death, workers have gone in unprepared or insufficiently protected.
TEST BEFORE ENTRY The stark reality is, wearing a gas monitor in a confined space is actually not enough to save you from many dangerous conditions that are immediately harmful upon entry, so pre-testing both the equipment you are about to use, and the atmosphere you are entering is critical.
Detailed in OSHA’s confined space standard 1910.146, it is recommended that before a worker enters a permit- required confined space, “the internal atmosphere shall be tested, with a calibrated direct reading instrument, for the following conditions in the order given: (1) oxygen content, (2) flammable gases and vapors and (3) potential toxic air contaminants.”
This ‘pre-entry’ testing must also test the atmosphere at the top, middle and bottom of the confined space as many toxic gases settle based upon their weight. Typically, the most lethal gases sit somewhere near the bottom of the confined space, so it is critical that testing is conducted at the recommended four foot intervals at the very bottom.
As atmospheric conditions within confined spaces can change quickly, it is also vital that testing is carried out throughout the day and this is where portable gas detectors come to the fore.
Lightweight, and small enough not to hinder a worker’s movement, portable gas detectors should be worn throughout a worker’s time in the confined space. If leaving the confined space for more than 20 minutes, for lunch or a coffee break for example, OSHA also recommends that a ‘re- entry’ test is conducted.
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