What's best for the situation?
We are a public facilities organization with 8 maintenance facilities technicians, in our portfolio of buildings we have the County Courthouse, Governmental Building, Health Department and others; it is not unlikely that once every couple of months we get a call from one of our buildings where someone has reported smelling gas (so far it has been the smell of a "dry drain" ) I am curious if anyone has ideas on how to responsibly respond to this type of report, short of evacuating the entire building.
We are considering getting a gas monitor of some type to put in the areas where the smell is commonly reported or possibly purchasing a gas digital meter readout for our maintenance supervisor.
Thanks for any ideas.
Comments (5)
Usually, the dry floor drains cause a build up of hydrogen sulfide (H2S), so a standard 4-gas meter should be able to detect the presence of the gas coming out of the drain. It can easily be prevented by having someone run water down the drains periodically to keep them from drying out. I'd recommend this as part of maybe a weekly or bi-weekly PM schedule for the areas/buildings.
As far as a response, as mentioned above, just get a 4-gas meter that has good resolution, accuracy, and low enough parameters to detect levels below 1 ppm because the odor threshold for H2S is <0.1 ppm in most cases. Make sure the people using the meter are trained on when/how/where to do the fresh air setup, T90 response times, etc. so they can actually get an accurate reading since meters aren't instantaneous (they usually take at least 10-15 seconds to produce an accurate reading on H2S sensors).
H2S has a vapor density of ~1.2, so it will accumulate in low-lying areas, so make sure they place the monitor close to the floor to check for readings. If your meter is only going off right at the drain or within a few feet of it, you can usually just pour some water down the drain to fix the "dry drain" issue, then place some portable blowers/fans in the area to dilute the air and get rid of the odor. If your meter is going off or you're getting readings that are close to 10 ppm (NIOSH's REL for H2S, which is what most meters alarm at) across the room or in other rooms, then I'd recommend evacuating the affected areas until you can do the actions just mentioned above.
Is the issue that people can't differentiate sewer gas from odorized natural gas?
I'm on a public hospital/university campus as we run into this all the time.
For us, Step 1 is knowing which buildings even have natural gas. We have a central steam plant, so many buildings don't even have in internal source for gas.
Step 2 is we send someone with both a 4 gas meter with an LEL sensor, and an combustible gas "sniffer". For us, 10 out of 10 times, even if there is a gas leak, it's well below the LEL for the room. If it's safe, we'll then use the sniffer to narrow down the location and then use soapy water to identify the exact location of the leak.
We have 24/7 EHS coverage along with our plant operations folks to facilitate this.
Step 3 is putting on a production of walking around the building putting people's minds at ease.
Great Job! Drew and Tim! On it as USUAL!