It's sulfur dioxide that is making the smell, not methane. Mercaptan is added to methane and natural gas to make that rotten egg smell because it is a sulfer-based chemical, just like naturally occuring sulfer dioxide is - which is what people are smelling. No doubt methane and other natural gases are being released along with the sulfer dioxide.
That's why the Salton Sea story is bogus too - sulfer dioxide/rotten egg smell is NOT the same as dead fish smell. AND the winds have been flowing AWAY from LA, not towards LA, from the Salton Sea.
I don't live in the LA area. But if I did, I'd be OUT of there TONIGHT, for a few days, enjoying the high country somewhere, and watching the news!
When I first smelled it I thought the was a skunk (animal or herbal).
Air Quality Officials Continue to Probe Source
of Widespread Sulfur Odors
September 10, 2012
Air quality officials are continuing to investigate the source of a rotten-egg odor reported last night and today across much of Southern California, from the Salton Sea to the San Fernando Valley.
“Several factors indicate that the Salton Sea may have been the source of these odors,” said Barry Wallerstein, executive officer for the South Coast Air Quality Management District (AQMD). “However we do not have any definitive evidence to pinpoint the Salton Sea or any other source yet.”
AQMD deployed field inspectors today to the San Fernando Valley, Long Beach, Colton, San Bernardino, Riverside, Perris, Temecula, Banning, Palm Springs, La Quinta and the Salton Sea in an attempt to locate the source of the odor.
Several sources have reported hot weather and a possible release of bacteria from the bottom of the sea due to winds there. Those conditions could cause strong sulfur odors.
In addition, strong thunderstorm activity in the Salton Sea area and resulting high winds from the southeast could have pushed odors into the Los Angeles basin. However, it is highly unusual for odors to remain strong up to 150 miles from their source, Wallerstein said.
AQMD will collect air samples this evening in several locations throughout the Coachella Valley and at the Salton Sea. An analysis of those samples may provide further evidence of a possible source.
Since midnight last night, AQMD has received about 200 complaints of sulfur- and rotten-egg odors. Most callers were from the Coachella Valley and other portions of Riverside County as well as San Bernardino and Los Angeles counties. Only a few calls came from Orange County.
A strengthening onshore breeze tomorrow may keep any additional odors from spreading as far west as they did today, AQMD officials said.
AQMD is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.
H2S smells like rotten eggs, not SO2. Got a 50 ppm cylinder sitting in my car.
The outflow boundaries pushed across the area from southeast to northwest last night, so it is probable that whatever the source of the smell is was transported within these outflow boundaries from thunderstorms. I just looked at the network of weather stations in the Coachella Valley and around 9:00 PM last night, winds up to 50 mph were measured throughout the network and were from a southeasterly direction.