Laboratory Gas Detection
The laboratory can be a dangerous place. From trip hazards, flammable materials and even bio-hazards. Furthermore, there are many aspects of risk minimisation that need to be considered to create a workplace that is both safe and compliant with health and safety legislation. One particular hazard that is common to many types of laboratory, from the life sciences, to physics research, is the hazards posed by gases.
Gases can be a chemical hazard in themselves, in the case of substances like Chlorine(1) and Nitrogen Oxides(2), which are corrosive and toxic. Therefore, to ensure compliance with COSHH regulations check occupational exposure levels in HSE document EH40 or the supplied MSDS. Even seemingly innocuous gases, like Nitrogen and Argon, which are famous for being chemically inert, can instead pose asphyxiation risks if leaks occur in poorly ventilated places. You must also consult ACOPs published by bodies such as the British Compressed Gases Association.
Another category of risk posed by gases used in laboratories is the explosion/flammability risk. Gases are typically stored in pressurised cylinders, and improper handling can lead to cylinder damage with sudden pressure discharge and explosions.(3) Any small spark from electrical equipment like vacuum gauges or hot surfaces can be sufficient to trigger a fire. Remember also that an Oxygen leak causing localised Oxygen enrichment will multiply the flammability risk many times over.
Furthermore certain gases also pose a toxic hazard for example, Carbon Monoxide (CO) and Nitrous Oxide (N2O). Toxic gases have Short Term Exposure Limits (STEL) of 15 minutes and Long Term Exposure Limits (LTEL) of 8 Hours. Toxic gas occupational exposure levels can be found on both the HSE EH 40 (or OSHA for US) or on the supplied MSDS sheets. It is a requirement to ensure employees are not exposed levels that exceed the STEL or LTEL.
These combined risks mean that is very important to be vigilant for gas leaks. In a laboratory setting, this will involve the installation and maintenance of appropriate gas monitors to warn of leaks. Audible and visual alarms will also be required. Multiple alarm types cater for differing user needs. For example a hearing impaired occupant may need to rely on visual alarms. Networked solutions, sometimes termed addressable systems, allow multiple devices as detectors, audible visual alarms and shutdown interlocks to be efficiently installed on one interlinked cable highway. As a result, this minimises cabling costs. At the same time these systems provide continuous integrity checks, quickly alerting to any faults which may go hidden on dated analogue type systems.
Two commonly used gases that pose their own detection and safety challenges are Oxygen and Carbon Dioxide. In Great Britain Carbon Dioxide has been classed as a ‘substances hazardous to health’ since 2002 (4). This means that there are recommended work-space exposure limits for both short and long term exposure. Therefore, in order to ensure worker safety and compliance with exposure limits, the installation of gas monitors is strongly recommended(5). Further to this there is specific guidance from the British Compressed Gas Association for Oxygen Alarm points. Therefore if you are not monitoring the environment for leaks you will struggle to show compliance to COSHH requirements and therefore also the Health and Safety at Work Act 1974. Furthermore, HSE document EH40 not only lists occupational exposure levels but also the required calculations to determine how long post exposure a person must recover in ‘clean’ air, if exposed to either the short term or long term exposure levels.
Many people wrongly assume the main risk of Carbon Dioxide exposure is asphyxiation. People mistakenly believe that, in settings where Carbon Dioxide and Oxygen monitoring are both required; an Oxygen depletion monitor is sufficient to cover both gases. However, doing this is in violation of the safety standard BS EN 60079-29-2:20156, which specifically states that “where carbon dioxide levels need to be monitored for safety reasons, a dedicated CO2 detector must be used”. This is because it is possible to exceed safe CO2 exposure limits still with sufficient oxygen concentrations that an oxygen depletion sensor would not trigger a warning. IGD offer CO2 sensors with a range of 0-5000ppm. This has a number of advantages over the industry standard of 0-5%V/V. For CO2 HSE document EH40 lists a long term 8 hour exposure at 5000ppm (0.5%)and a short term 15 minute exposure at 15,000ppm (1.5%).