why did so much of Philadelphia smell like gas yesterday?

June 25, 2014 6:12 PM

Yesterday morning it smelled like gas from South Philly though center city and up into Fishtown, but it wasn't actually natural gas. What was it?

When I walked the dog in Penn Treaty park yesterday morning, it smelled like natural gas. The smell seemed to be strongest when the wind was blowing, and it was coming from the south and off the river. When I got off the el at Suburban Station, it smelled like gas, and one coworker noticed it at 8th and Arch. Two coworkers who live in South Philly east of Broad also smelled gas that morning, and one had the night before. Monday night the gas company tested her entire block and found no gas. The other coworker saw the fire department responding to a call from a bakery about the gas smell three blocks from their house. That was also not actually natural gas. A third coworker said his apartment in old city started smelling like cat pee Monday night, which was perplexing as he doesn't have a cat. We thought it was likely the same smell.

Google and the news didn't have anything about it, but I did find an article about a similar thing happening in January when people smelled not-gas over "a swath of territory that stretched from Germantown through Northeast Philadelphia into lower Bucks County". Also found references to a not-gas smell across south Philly in December of 2009. Both said that PGW didn't know what the smell was.

Theories in the office were that one of the chemical plants or refineries had released something into the sewage where it was reacting at the water treatment plant (apparently this is a thing) or into the air. But what? What else are the natural odorants used for?

posted by sepviva to Science & Nature (11 answers total)

Weird- I didn't think anything of it at the time but I smelled a very faint urine-y smell most of yesterday. I thought it was just my allergies (or meds for same) playing havoc with my nose. If the data point is helpful at all I was in art museum/Fairmount all day.
posted by Merzbau at 6:24 PM on June 25, 2014

Best answer: Natural gas is odorized with mercaptan, also known as methanethiol. A good summary here, that even explains why Merzbau thought they were smelling urine.

The distinctive smell of mercaptan comes from sulfur, which the human nose is very, very, very good at detecting. Pretty much anything sulfurous, be it artificial or merely rotting food, could have triggered your sense yesterday. Here's a list of occurrences of methanethiol in our world, all potential candidates for yesterday's scent event.

Anecdotally, I once lived in a building that also provided subsidized housing for medical students, and I was on the verge of reporting a natural gas leak (as well as panicking and decamping) when they told me that they had been synthesizing methanethiol in lab and brought home the smell on their clothes.
posted by telegraph at 7:10 PM on June 25, 2014

I didn't smell it and hadn't heard anything, but I saw this: Southwest Philadelphia Residents Want Answers After Gas Outage
posted by zachxman at 7:28 PM on June 25, 2014 [1 favorite]

Anecdotally, this is how summer in the city smells to me. I've lived or worked in the city for years, and hot humid days in the summer normally smell like a variation of sewage etc. I never thought about this beyond the obvious -- sewage lines get heated and the warm air carries the odor through the storm sewers and up to street level.
posted by DoubleLune at 10:17 PM on June 25, 2014

I didn't notice anything myself, but one of my cast members did mention that our rehearsal space in Rittenhouse smelled a little more....smelly....than usual. I know there was a steam leak around the convention center on Monday, but that may have nothing to do with it. Could just be the heat and humidity combined with the way our rivers normally smell.
posted by picklesthezombie at 6:07 AM on June 26, 2014

Response by poster: This was definitely not the usual summer city stink. Unfortunately my coworker who has worked at the water treatment plants didn't smell it to compare, but I don't think it was sewer smell. Telegraph's link suggests it could be a product of oil refining, and I know the refineries do belch things out sometimes.
posted by sepviva at 8:27 AM on June 26, 2014

Something similar happened in a section of my city a few years back, and it turned out that a train carrying mercaptan through the city had a leak. A coworker who lived in one of the affected areas reported the smell, and the person at the gas company explained about the train and wearily added that they were getting calls aaall the way along the track.

Now, if I could just figure out why an area near my work often smells like mothballs...
posted by telophase at 8:44 AM on June 26, 2014

Things in Phila that take on a new olfactory form in 90ish degree heat:

Trash
Standing water (so many alleys with algae farms, tires abandoned)
Any type of food processing facility (Dietz and Watson makes my whoel neighborhood smell like hot dogs, which is oddly comforting)
Refineries / Chemical Plants
Air coming up from the subway
Exhaust from restarunts that use a lot of fryer oil (chinese takeout)
Fryer oil collection containers behind fast food joints.
Dust
Animal / human waste outside
Any type of berry or fruit from a tree or bush that falls on the ground in mas quantity and ferments there.
posted by WeekendJen at 11:27 AM on June 26, 2014

I think it must be what zachxman says.

From his link:

PGW says the gas had to be cut after a water main broke on Saturday at 56th Street and Woodland Avenue. The company says water got into gas lines and has to be removed. So far, workers have taken out up to 40,000 gallons. The outage reaches as many as 10 city blocks.

PGW almost has to be blowing the water out of its lines with its own gas and venting it to the atmosphere, where you are then smelling it.
posted by jamjam at 11:53 AM on June 26, 2014

I smelled it to when I left my house (Graduate Hospital neighborhood). I called to report it,which I wouldn't normally do but with the recent house explosions it seemed prudent. I was transferred from 911 to the fire department to PGW. No one was helpful or knew what had happened but they all commented that many people were calling in.
posted by mmm at 5:54 AM on June 27, 2014

Response by poster: A similar but worse smell has been around at times recently, and it's not just summer city stink, at least according to PGW and the air quality management office. The Passyunk Post had two articles recently about it.
http://www.passyunkpost.com/2014/07/21/city-blames-new-jersey-for-sulfuric-urine-like-mystery-odor
posted by sepviva at 11:07 AM on July 24, 2014 [1 favorite]