Best Practices for Use of Portable Gas Monitors in Confined Spaces

In the confined work spaces found in chemical plants, paper mills, refineries, underground mines and utility passageways, the air may be contaminated with toxic or combustible gases or suffer from a lack of oxygen. Regulations call for the monitoring of these environments.

Every day, workers who are just doing their jobs can come into contact with airborne contaminants that are harmful or even fatal. This especially is true of workers who must enter confined spaces to perform job tasks.

To protect workers, employers are required by law to have a way to monitor the air before entry and during the entire time employees occupy the confined space. Employers must ensure a safe and healthy worksite to maintain production and to protect their workers.

Each person entering the confined space should be equipped with a portable gas monitor worn where it can be checked easily and frequently. It’s a must-have, life-saving tool that can be used in a wide range of industrial settings.

Gas Monitor Design

Portable gas monitoring systems may be designed for a single substance, or can be fitted with multiple sensors. Some measure up to six gases and include piercing audible and attention-getting 360-degree visual alarms.

An alternative or adjunct to personal monitors is a transportable area monitor. Look for one with area monitoring via diffusion or with a sampling pump, wireless communications capabilities and a waterproof housing with continuous operation of around 60 hours. More run time helps increase productivity by minimizing new checks of the atmosphere for each shift change or when the space may be unattended. A multiple sensor design often is driven by OSHA requirements, which specify confined space monitoring by following this detection sequence: oxygen, combustible gases and any potential toxic contaminants (see 29 CFR 1910.146(c)(5)(ii)(C)).

Portable gas monitors are lightweight with dimensions similar to a mobile phone for ease of use. They run on either rechargeable or replaceable batteries.

Sensors Are the Heart of a Gas Monitor

As you might imagine, the sensor is the most important component inside a gas monitor. When facing an unknown gas hazard, you need a sensor that provides dependable detection of combustible atmospheres. It quickly should respond to explosive gases and have a high level of sensitivity to combustible organic vapors in a confined space. The monitor you choose should include sensors for:

➤ O2 – To check the oxygen level for deficiency or enrichment.

➤ Combustible gas – To test for levels of flammable or explosive gases.

➤ Toxic gas levels – Typical confined space monitors have hydrogen sulfide (H₂S) and carbon monoxide (CO) sensors; additional toxic sensors may be used based on the application.

Gas monitors also provide an alarm at the appropriate real-time concentration, short-term exposure limit (STEL) or time-weighted average (TWA) for the monitored substance.

Electronic gas monitors with four or five different sensors (multi-gas monitors) may be sufficient for many confined space applications. Some situations may require monitoring capabilities for additional substances. As a general rule, each type of sensor is best suited for certain substance categories.