【2026 Instrumentation Technology】Key points for setting up area alarms for flammable and toxic gases

This post was last edited by The one on 2026-5-15 11:13. Clear activation signal: Choosing the activation signal for area alarms is one of the more confusing issues in settings. It should be clear first that the activation signal for the regional alarm should use the second-level alarm setpoint signal.

Therefore, the standard requires that an alarm be activated in the area affected by a level 2 alarm, while a level 1 alarm is generated by the integrated alarm built into the detector, and is primarily used to alert nearby inspection personnel to pay attention and take action； Only when the gas concentration continues to rise and reaches the secondary alarm setpoint does the area alarm activate, issuing a warning to the people in the entire area. In this way, primary alarms and secondary alarms have a clear division of roles, forming a well-structured early warning system.

This post was last edited by The one on 2026-5-15 11:14. Ensure full coverage of sound and light: Regarding the number of area alarms and the requirements for sound and light, there is only one core principle – full coverage with no blind spots. It is to ensure that people within the alarm area can clearly detect the alarm signal, no matter where they are standing. In actual engineering design, it is necessary to take into account factors such as the floor area occupied by the equipment, the layout of devices and structures, the physical and chemical properties of the emission sources, as well as the characteristics of air flow at the site, in order to determine appropriately the number of area alarms and their installation locations.

This post was last edited by The one on 2026-5-15 11:14. Choosing the right installation location: The location where the area alarm is installed directly determines how effective it will be. The area alarm in the field should be installed as close as possible within the alarm zone where the detector is located; its installation height is generally 2.2 meters above the ground or floor of that area, so as to be easily visible to the staff and facilitate regular maintenance. Additionally, the installation location should be avoided in areas with high vibration and strong electromagnetic interference to ensure the stable operation of the equipment. For outdoor installation, attention must also be paid to the protection rating, with measures such as wind and rain protection as well as sun protection taken.

The area alarm is the \"last line of auditory defense\" for workers on site; it must not fail to sound. Paying attention to it means prioritizing one’s own safety.

The following response is for reference: \"Flammable and Toxic Gases in Petrochemical Industries\" (GB 50493-2019), 3.0.4 – Audio and visual alarms for flammable and toxic gases should be installed in the control room operation area； On-site area alarms should be installed based on the area occupied by the equipment, the layout of the devices and structures, the physical and chemical properties of the emission sources, as well as the characteristics of air flow at the site. Such alarms must have both audible and visual warning functions. Explanation of the provisions: 3.0.4 Installing audible and visual alarms for combustible gases and toxic gases in the control room operation area helps the operators there to detect such hazards promptly and take appropriate action. To alert on-site staff, area alarms are typically installed at the main entrances and exits of the production site as well as in areas with high noise levels【where noise exceeds 85 dB(A)】. In relatively enclosed areas such as compressor rooms, pump rooms, silos, analysis booths, and laboratory rooms where inspections are carried out and where the accumulation of flammable or toxic gases may occur, audio-visual alarms should be installed in prominent locations at the entrances and exits. Its purpose is to remind inspection personnel to be cautious when entering these areas.

In terms of sound level, the alarm signal level of area alarms should be above 110 dBA, while the total sound pressure at a distance of 1 meter from the alarm should not exceed 120 dBA; this is to prevent hearing damage due to being too close to the alarm during wiring or debugging. There is also a practical requirement: the alarm sound level of the on-site alarm should be 15 dBA higher than the background noise level. In other words, when making a selection, it is necessary to determine the noise level at the site to ensure that the alarm sound can be clearly heard even in a noisy environment.

Regarding the optical alarm, the optical component of the audible and visual alarm should use a pulse-based alert system, with the pulse flashing frequency ranging from 60 times per minute to 120 times per minute. The effective luminous intensity of light alarms designed for outdoor use is generally not less than 300 cd; this brightness is roughly equivalent to that produced by 300 ordinary candles burning together, and it is sufficient to penetrate the rain, fog, and darkness in chemical plant areas ； The effective luminous intensity of the optical alarms used in the factory buildings is generally not less than 150 cd. Different types of alarms should also be distinguished by color; typically, fire alarms use red, gas alarms use blue, and accident alarms use yellow.

Management recommendations for area alarms: First, establish a standardized ledger for managing alarm zones. Based on the actual conditions of the installation, alarm zones are established according to the devices or units in the production and storage and transportation facilities. Information such as the list of detectors in each zone, the setup of area alarms, and the hierarchy of activation signals is specified, ensuring clear zoning and complete records.

Second, conduct regular functional tests of regional alarms. For area alarms, regular audio and visual function tests should be conducted to verify that the sound level meets the requirement of being 15 dBA above the background noise level, and that the flashing frequency and brightness of the optical alarm are within acceptable ranges.