Understanding signal and actions associated with monitoring systems

An electrochemical sensor is the most practical type of H2S detector because it responds in seconds to a gas exposure. Still, when selecting such a sensor, be sure it has the sensitivity and accuracy needed to support the new H2S guidelines.

Industrial hygiene safety programs exist to create and maintain a safe, healthy workplace for employees, and the new ACGIH recommendations are no different. While these recommendations are expressed in terms of an eight-hour TWA and 15-minute STEL, most companies are likely to set action points in their safety and hygiene procedures based on instantaneous exposures or one-minute average ceiling limits, as read from an electronic sensor. With that type of procedure, the detector alarm level would probably be set somewhere between 1 ppm and 5 ppm and would require unprotected workers to immediately evacuate the area when the alarm goes off or don SCBA gear.

Important Features in Portable/Personal Monitoring Equipment

• Look for the ability for several sensors to be installed in the unit that can be selected from a list that includes CH₄, H2S, SO₂, CO, O₂, H2, NH₃, HCN, NO, NO₂, and others.
• Simple bump test station and a traceable bump test mode; bump testing every day is recommended to check sensor accuracy, stability, and response time and verify proper operation of the display and alarm functions.
• A variety of power supply options: Lithium alkaline or rechargeable NiMH battery supplies with charging module and charger are popular ones.
• Built-in event or data logger with an optional USB adapter and cable so that the personal monitor can output exposure data to a PC for analysis and reporting.