Hydrogen Sulfide Alarm Settings

Guidance currently exists on the hse website for setting alarm levels for predominantly flammable gas detectors.

Hydrogen sulfide alarm settings.

This white paper presents information on the health effects of h 2 s. Provided standards exist all alarm settings are based on the following. The post below is from a real client case and shows how hydrogen gas can trigger these alarms and potentially become an explosive hazard. In the past the most widely recognized occupational exposure limits for hydrogen sulfide h 2 s have referenced an 8 hour twa of 10 ppm and a 15 minute short term exposure limit stel of 15 ppm.

Lel ch4 0 to 60 and 0 to 3 0 by vol ch4. When these detectors sense high levels of hydrogen sulfide they alert you with an audible alarm warning light and vibrating alarm. It detects hydrogen sulfide in 0 20 ppm 0 50 ppm or 0 100 parts per million ppm levels over a wide temperature range. All alarm set points are field adjustable over the full range of the sensor exceptions.

Monitoring hydrogen sulfide h 2 s to meet new exposure standards st 9660 2007 abstract in order to better protect workers from exposure to hydrogen sulfide h 2 s acgih modified the threshold limit value tlv for this chemical in 2010. Hydrogen sulfide and hydrogen sulfide monitoring instrumentation. While the hydrogen nulled sensor takes a little more time to recover after exposure the time to alarm is virtually the same for both sensors. The unit features one person calibration and can virtually self calibrate by simply activating a magnetic switch and applying gas.

In february 2010 the american conference of governmental industrial hygienists acgih adopted a new threshold limit value tlv recommendation for h 2 s lowering the 8 hour twa to 1 0 ppm. Similar guidance does not exist however for toxic gas detectors although alarm levels are specified for a limited number of gases in specific industries e g. Chlorine plants hydrogen sulphide offshore. Carbon monoxide alarms are vital pieces of safety equipment used to protect workers and residents from poisonous carbon monoxide gas.

Using this procedure h2s meters are typically set to alarm at 10 ppm and action is taken to reduce exposure usually by leaving the area or by using scba equipment when air concentrations go. The third chart compares the performance of the gfg 2cf hydrogen nulled sensor and a standard gfg 4cm co sensor exposed to 200 ppm co calibration gas. You can adjust the alarm trigger point to suit your environment. Depending on individual circumstances an alarm 1 setting of 2 and alarm 2 setting of 5 seem appropriate.

No doubt 5 ppm should be one of the alarm set points on a dual alarm unit and should be the setting on a single alarm equipped instrument. But did you know that hydrogen gas from charging batteries can set off the alarms as well. High alarms are based on 2 times osha pel values.