NFPA 37 Section 4.1.2.2.3 (2015) - Hazardous Vapor Detection System

[Shujinko]

A question. Does anyone know of a hazardous vapor detection system compliant with NFPA 37 Section 4.1.2.2.3 (2015)? Does anyone know a manufacturer that would have this type of system under their line of products?? I want to tie the hazardous vapor detection to an exhaust fan in a detached generator building, based on the amount of hazardous vapors present. I don't have any experience with these types of systems.

4.1.2.2.3* Dedicated detached structures shall have ventilation designed to prevent a hazardous accumulation of flammable vapors or gases, both when the engine is operating and when it is shut down.


A.4.1.2.2.3  Explosion venting for a fuel explosion should be considered for large engine installations. In some installations where it might not be practical for the normal constantly operating ventilation to prevent the accumulation of flammable vapors or gases from leakage, a hazardous vapor detection system can be installed. The system is often set up to detect the hazardous vapors at two concentration levels (percentage of the lower explosive limit, LEL).

If the first (lower) level is reached, the ventilation volume is increased by use of a purge fan to remove the vapors. If the second (higher) level is reached, the operation is shut down and the enclosure inverted as the ventilation is stopped. The inverting is normally done quickly and maintained until the leak is stopped, after which the entire hazard volume is purged while operations are resumed.

 

[paulengr]

There are lots of gas detectors but it is gas specific. Look for Instrument
Engineers Handbook by Liptak which has a whole section describing the types, vendors, and costs.

 

[DM2-Inc]

We provide these system but those that specify them are often vague on the requirements.
Our typical design is based on:
- The system has battery back for (typically 8 hours)
- Is tied into the fan to turn it on.
- Often tied into a shut trip if the electrical equipment in the area isn't classified
- Tied into a local alarm system (fire, plant, etc.)
- Has colored warning lights for different types of gases (there are no standards for light colors based on the type of gas).
- If the area already has an HVAC PLC, or other PLC, the detector could be interfaced there. Normally that detectors have 4-20mA analog output.
- Detectors are available with or without relays. There are usually 3 relays (Falut, Low Gas, or High Gas). If you have multiple detectors, you're better off connecting them to a PLC than controlling the fan directly from the gas detector.

 

[Shujinko]

We provide these system but those that specify them are often vague on the requirements.
Our typical design is based on:
- The system has battery back for (typically 8 hours)
- Is tied into the fan to turn it on.
- Often tied into a shut trip if the electrical equipment in the area isn't classified
- Tied into a local alarm system (fire, plant, etc.)
- Has colored warning lights for different types of gases (there are no standards for light colors based on the type of gas).
- If the area already has an HVAC PLC, or other PLC, the detector could be interfaced there. Normally that detectors have 4-20mA analog output.
- Detectors are available with or without relays. There are usually 3 relays (Falut, Low Gas, or High Gas). If you have multiple detectors, you're better off connecting them to a PLC than controlling the fan directly from the gas detector.

What's the name of the manufacturer(s) of this system? Can you send me a website? I appreciate it.

 

[DM2-Inc]

These are custom solutions that we manufacture using a variety of different brands. This isn't something you can buy off a shelf from a manufacture. With regard to equipment, we mostly we use Honeywell and Detronics.