Upper and lower limits of chlorine gas alarm

When selecting the product, inform the manufacturer about chlorine as the medium, and set the lower limit at 25% LEL, where LEL refers to the lower explosive limit of flammable gases. There’s no need to set a limit.

Thank you, but the person upstairs mentioned flammable gases, while I was talking about toxic gases

This post was last edited by hnxao on 2009-6-19 23:46. Regarding the setting of the alarm thresholds for chlorine gas detectors, many organizations are confused about this issue; here are my thoughts on it: According to GBZ 2-2002, the maximum allowable concentration (MAC) of chlorine gas is 1 mg/m3, which can be converted to 0.3 ppm as mentioned by the poster. Additionally, in the past, the standard used TLV to indicate the maximum allowable concentration of harmful substances in workshop air. SH3063-1999 stipulates that \"the measurement range for toxic gases should be 0~3 TLV.\" It also stipulates that \"the alarm setting value for toxic gases should be less than or equal to 1 TLV; when it is difficult to prepare standard gases for testing, the alarm setting value can be below 2 TLV.\" The range of chlorine detectors available on the market is generally 0–10 ppm or 0–20 ppm. In other words, both of these ranges exceed the requirements specified in the SH3063-1999 standard, which is “0–3 TLV”, corresponding to approximately 1 ppm. According to available data, the sensitivity of chlorine sensors can reach 0.02–0.2 ppm; therefore, if the measurement range is 0–20 ppm, it is feasible to divide this range into 100 increments. But why can’t the alarm threshold be set lower? This is because chlorine is highly unstable, and it is difficult to store low-concentration standard gases, which makes it hard to accurately set the alarm points (0.3–0.6 ppm) as required by the SH3063-1999 standard. As we all know, it’s even more dangerous when uncalibrated alarms cause misguidance! Currently, various units generally set the alarm threshold at a range of 0.5–2 ppm or 2–5 ppm, depending on the range of the chlorine gas alarm. Let’s take a look at two references regarding the effects of different chlorine concentrations on the human body: Reference 1: Degree of harm caused by chlorine concentration (ppm/m3): 0.2–0.5 – no adverse effects; 0.6–1.5 – slight odor; 1–3 – strong odor, irritation to eyes and nose; 6–18 – irritation to throat; 30–90 – coughing; 40–60 – 120–180 – inability to breathe, loss of consciousness, death within 30–60 minutes; 100 – 300 – immediate difficulty breathing, reduced pulse rate, cyanosis, fatal damage; 900 – 2700 – immediate death; 10,000 – 30,000 – ordinary filtering gas masks become ineffective. Reference 2: Gas name, gas concentration (ppm), effects on the human body: Cl2 – 0.5 is the allowable exposure level (OSHA, ACGIH). 3 Irritates the mucous membranes, eyes, and respiratory tract. 3.5 Produces a noticeable foul odor. 15 Immediately stimulate the throat. 30 Maximum exposure concentration within 30 minutes: 100–150. Causes chest pain and a feeling of pressure; prolonged exposure can lead to death. Additionally, the information below, taken from NIOSH (National Institute for Occupational Safety and Health in the United States) (http://www.cdc.gov/niosh/idlh/intridl4.html), can also be referenced: Substance, Original IDLH Value, Revised IDLH Value. For chlorine, these values are 30 ppm and 10 ppm respectively; NIOSH provides specific figures at http://www.cdc.gov/niosh/idlh/7782505.html. IDHL (Immediately Dangerous to Life or Health concentration) refers to the concentration at which air pollutants in the environment reach a dangerous level, such as one that can be fatal or cause permanent health damage, or that prevents people from escaping immediately. The IDHL value is mentioned here because the new version of the \"Code for Design of Detection and Alarm Systems for Flammable and Toxic Gases in Petrochemical Industries\" GB50493-2009 (implemented on July 1, 2009) has redefined the range and alarm settings for toxic gas detectors: \"The measurement range for flammable gases is 0~100% LEL.\" The measurement range for toxic gases should be 0~300% MAC or 0~300% PC-STEL ； When the measurement range of the existing detectors does not meet the requirements, the measurement range for toxic gases can be 0~30% IDLH. “The alarm setting value for toxic gases should be less than or equal to 100% MAC/PC-STEL; when it is difficult to prepare standard gases for testing, the alarm setting value may be below 200% MAC/PC-STEL. When existing detectors cannot meet the aforementioned range requirements, \"the alarm setpoint for toxic gases (high-high limit) shall not exceed 10% of the IDLH value.\" According to China’s current standard GB18664-2002 on the selection, use, and maintenance of respiratory protection equipment, the IDHL value for chlorine is still set at 30 ppm; therefore, the alarm threshold for chlorine detectors can be set up to 3 ppm. However, based on the revised data from NIOSH, it should be set around 1 ppm. Therefore, taking all factors into consideration, it is appropriate to set the alarm threshold for chlorine detectors at 0.5–2 ppm.

Our unit is generally set at 1 ppm, while in places with stricter requirements it is set at 0.3 ppm

According to the standards, it should be 0.3; however, taking into account factors such as the minimum detection accuracy of the integrated instrument, if you don’t mind the annoying alarm sound, you can set it to 0.3. Generally, it is set to 1.

Where can I download the **standard

I have a question: shouldn’t mg/m3 be equivalent to ppb? That can’t be in the same order of magnitude as ppm, right?

Also, our company has set it at 0.35 ppm