Worker safety and a facility's security can depend on choosing the right portable gas detector. There are several factors to consider before deciding which detector fits your needs.

The first thing you need to do is determine which atmospheric hazards are, or could be, present. Consider the existence of combustibles, toxic gases and volatile organic compounds (VOCs), and the possibility for oxygen enrichment or deficiency. Once you have identified the atmospheric hazards, you can then decide whether you need a single or a multi-gas detector.

It is important to make sure the instrument you choose for an application can support the number and type of sensors you will need. Most confined-space instruments include an oxygen sensor, a catalytic flammable/combustible gas sensor, and one or two electrochemical sensors for detecting specific toxic gases. Some instruments also incorporate an infrared sensor for carbon dioxide or methane.

For the record

You might require a record-keeping feature in the detector, and event logging and data logging come as standard with certain instruments. Data logging instruments are usually set up to keep monitoring information whenever they are switched on, and this information can be crucial for compliance and record keeping. Data logging instruments are also useful in the event of an accident or unusual occurrence, as they provide a snapshot of the conditions at the time of the event. Documentation of proper use could significantly reduce your liability if things go wrong.

Calibration and bump testing (also known as challenge or function testing, to check the detector is working properly) should be straightforward. Most data logging instruments automatically update and store dates and other calibration information. Many manufacturers now offer automatic calibration or docking stations that calibrate, recharge and store calibration records. It is worth enquiring about the availability and cost of calibration and docking stations before you buy the equipment.

One-button operation is useful, especially when the user is wearing gloves. Other specifications include operating temperature and humidity range. Size and weight will also be factors; two detectors might measure the same gases, but one may offer more features while the other may be smaller and lighter.

Portable instruments may use disposable alkaline batteries, rechargeable batteries or both. If the battery is a proprietary design (that is, not a standard shape) check the availability and cost of replacements. If the instrument takes a rechargeable battery, does the price include a battery charger?

There are basic disposable "plug-and-play" models that do not require any sensor or battery replacement, and arrive fully calibrated.

Accessorising

The availability of accessories can make using a detector easier in certain situations, and it's worth checking if these accessories are included. Check the availability of sample draw kits and motorised pumps if your users will be sampling from remote locations. Other useful accessories include hard-hat clips, carry cases, training videos and calibration materials.

Portable gas detectors need to be durable. Check the certifications and standards of the device you are considering before you buy. Ingress protection, or the IP66/67 rating on a product, can identify that an instrument has been tested and is dust-tight and water-resistant (to both water jets and immersion). This test certification further demonstrates the detector's ability to perform reliably in harsh industrial environments.

The ATEX Directive embodies the European requirements for equipment used in potentially explosive atmospheres, while CE marking is the manufacturer's declaration of compliance with all applicable directives. For most products sold in the EU, CE marking and a Declaration of Conformity are mandatory.

Whatever criteria you use in choosing your portable gas detector, you should always try out the instrument in the field. There is no substitute for seeing how an instrument will perform under actual use conditions.

Most leading manufacturers, or their distributors, have evaluation instruments available to try. Sometimes you can rent instruments before you buy them. Choosing a portable gas detector is a safety-critical decision. Assessing  the specifications and versatility of the detector, and checking the equipment's approvals and certification, will help determine which instrument best fits your needs.

Sarah Ursulan is marketing manager at BW technologies, suppliers of gas detection equipment, www.gasmonitors.com