GAS DETECTION FOR SAFETY

Recent, stiffer legislation has spawned an abundance of new gas detection equipment

by Mark Burrp

Processing is an area where the need to control hazards at work is absolutely paramount, since potentially dangerous concentrations of gases can easily be found. So systems specifiers and designers need to be aware of the up-to-date legislation and the equipment which is available to provide compliance.

There are many different gas detection technologies, including electrochemical and catalytic instruments, paper tape instruments, solid state and, more recently, particularly sensitive Fourier-transform infrared equipment. And all of these are blesssed with their advantages – but also disadvantages.

The requirements of The Control of Substances Hazardous to Health (CoSHH) Regulations to safeguard the health of employees are underlined in recent European Regulations, like EN689.

Three-fold sampling

EN482 states that it is the user’s primary responsibility to choose appropriate procedures or devices. The type of equipment used will very much depend on the sampling strategy. HSE Guidance Note EH42 defines sampling in three ways:

* The first level of sampling uses a preliminary survey to indicate whether an exposure problem exists and, if so, to determine the seriousness of its implications.

* The second level of sampling uses detailed surveys to provide comprehensive data on the levels of exposure and the exposure patterns. This level of sampling will feature automatic gas detection pumps, multi-gas instruments and fixed gas detection systems.

* Rarely used, the third level of sampling is intended for complex sampling programmes, or where an unusually high degree of accuracy is required.

Equipment for a wide variety of sampling methods is available, from personal monitors to detector tubes and fixed gas detection systems. Whichever system is used, however, it is vital that full training in its use and analysis is provided to ensure accurate results.

Sampling methods include lapel badges, short term tubes for monitoring personal exposure, spot check measurements, leak checks, confined space investigation, etc. Microprocessor controlled, battery operated bellows pumps are also available for use in potentially explosive atmospheres.

Sampling tubes

Short term, long term, diffusion and sampling tubes each have a specific role to play in indicating the exposure of personnel to contaminants, depending on the location and specific environment.

In addition, there are personal single gas monitors, which are both simple to use and small in size. These hand-held instruments can be used to monitor a broad range of gases, including carbon monoxide, hydrogen sulphide and the spread of flammable gases.

Sophisticated in operation, some instruments combine microprocessor controlled intelligence with a continuous display of gas concentrations – and easily identifiable high and low levels as well as time weighted average (TWA) alarms.

High performance multi-gas measurement instruments can be used to measure a wide variety of gases in virtually any application, from indoor air quality for confined space entry or to monitor landfill gases. They feature individually adjustable visual and acoustic alarms and, in response to industry’s increasing demand for detailed exposure, a data logging facility.

Fixed detection

Designed to provide workplace monitoring, fixed gas detection systems can be used to monitor remote areas and multiple sites.

The advantages of today’s instruments in terms of easier calibration and ease of use include microprocessor control, offering self diagnostics and fail-safe operation. Typically, gas detection instruments are supplied complete with liquid crystal displays and operator keypads, making them ideal for one-man calibration.

* The Author is with Draeger.