Gas detection technologies have improved dramatically in recent years. These days, portable gas detection for recording and monitoring exposure may include microprocessor-driven electronics, next generation signal processing, state-of-the-art battery choices and enhanced data manipulation and storage. Faced with all of these improvements, how should safety professionals select the product that's best for their workplace? I'm not a scientist, but I've spent a lot of time researching the options and identifying their pros and cons. Let me tell you what I've found.

Selecting Proper Gas Detectors

Without proper gas detection, hazardous atmospheres may significantly affect the health and safety of workers. Many airborne contaminants cannot be detected by smell or vision and can only be measured with special equipment. Depending on its sensor configuration, proper gas detection equipment can help identify the hazard and protect your workers.

Selecting a gas detector should be based on the hazard encountered. For example, in confined space work, it is necessary to monitor for oxygen deficiency/enrichment, combustible gases and toxics. Therefore, it's necessary to choose an instrument capable of dealing with these issues.

Unfortunately, too many purchasers make large and crucial equipment expenditures without really understanding what they are buying. Sensors and their capabilities are the single most important factor when choosing a gas detector; yet more often than not, decisions are based on size, price and other features that have nothing to do with the instrument's detecting abilities.

The Three Categories of Gas Monitors

There are many federal, provincial/ state and local safety and environmental regulations requiring hazardous gas and vapor monitoring. Most (but not all) requirements fall into three categories:

• Personal exposure monitoring;
• Confined space entry; and
• Ambient air monitoring

Let's take a brief look at each of these.

1. Personal Exposure Monitoring

Personal exposure monitoring is the detecting of toxic gases in an individual worker's breathing zone. Alarm settings on monitoring instruments generally relate to the physical and toxic characteristics of a specific gas and/or regulated threshold limits.

The American Conference of Governmental Industrial Hygienists (ACGIH) recommends measuring exposures by threshold limit values (TLV), such as the 8-hour time-weighted average (TWA) and the 15-minute short-term exposure limit (STEL).

Occupational Safety & Health Administration (OSHA) measures with permissible exposure limits (PELs), some of which are based on TLVs. In Canada, PELs are set by provincial Occupational Health and Safety (OHS) regulations. The provincial PELs are similar to those adopted by OSHA in the U.S.

Some monitors are equipped with alarms that measure yet another set of limits called "immediately dangerous to life or health" (IDLH).

2. Confined Space Entry

In general, confined space regulations require that air in a confined space be evaluated for the presence of combustible gases before any worker enters the area. Gases detected must be in the lower explosive limit (LEL) range, with less than 10 percent LEL typically considered an acceptable concentration. This percentage may change depending on whether hot work is to be performed within the confined space.

The space must also be measured for oxygen deficiency or enrichment: 20.9 percent oxygen volume in air is generally considered clean air; 19.5 percent is low (deficient); and 23 percent is too high (enriched).

Finally, the space must be tested for the presence of specific toxic gases, which must be within defined applicable concentration ranges, typically parts per million (PPM) or parts per billion (PPB).

Note: Before setting any sensor alarms, refer to your applicable legislation and verify legal requirements.

3. Ambient Air Monitoring

Ambient air monitoring involves continuous measurement of any workplace air to which workers are exposed - indoors or out. Normally, permanent monitoring systems are used for ambient air monitoring, although it can also be done with portable instrumentation set up to detect specific gases.

The Two Types of Gas Detection

There are two categories of gas detection instruments:

• Indirect reading, where samples must be sent to the laboratory for analysis; and
• Direct reading, which provides information at the time of sampling.

Direct reading instruments are the only safe source of sampling information in operations where the primary objective of gas detection is to immediately warn a worker of adverse atmospheric changes.

Conclusion

There are a number of direct reading portable gas detector manufacturers in the market today. Their product lines come in a variety of sizes, shapes, colors and sensor configurations. Next week, we'll look at various combustible gas sensors and discuss their pros and cons.

SUMMER SAFETY

Fire up the mood, not the yard

Safety by Candlelight

By Catherine Jones

There are few things more relaxing or romantic than a summer evening on the patio -  the hammock, the friends and the mood lighting made possible by pretty torch candles positioned around your garden.

Not to spoil the mood, but be careful with these things. Health Canada has issued a reminder that as with all candles, torch candles - whether used for ambiance or bug control - must be handled with care. Remember that embedded in the wax is a support stake, a fragile piece of wood that may catch on fire or break and allow a lit candle to fall.

Keep the flame contained - and your evening relaxed - by following these few pointers:

• Don't use torch candles indoors. They're for outdoor use only.
• Secure torch candles in a bucket of sand and place them far from any object (including flowers, shrubs or trees) that may catch on fire.
• Keep kids and pets away from burning candles.
• Don't use torch candles in windy conditions.
• Don't group torch candles.
• Before moving a candle, extinguish it and wait for the wax to cool.
• Watch for signs that the candle is not burning correctly. If your torch candle emits a high or intense flame or starts crackling, put it out immediately.
• Don't blow out the candle. This can spread sparks and hot wax. Instead, use water or a snuffer to extinguish the flame.
• After extinguishing the flame, turn the candle upside-down in a bucket of water. Even candles with little smoke and no flame can start a fire.
• When the candle has only 2 inches of wax left, put it out.
• And, of course, never leave a burning candle unattended.

Source: Health Canada

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