In the Environmental Chemistry course, I've just yesterday wrapped up water, which we've been wading through, or joyfully splashing about in, depending on whether you're a student enrolled or me having been given carte blanche to talk about whatever seems interesting. In a wrap-up lecture on natural water quality, I mentioned Henry's constant for methane, pointing out that was why it bubbled up from the bottom of stagnant pomds. I forebore to mention (because I was immersed in the water) that methane is lighten than air and so rapidly disperses over such swampy ponds and bayous. It's a different matter in mines where methane is known as firedamp and has killed thousands of coal and other miners other the years. Even as I write, I feel I should write me a lecture on methane for early next year.
With that in my mind, I perked up when the wikipedia "on this day" section mentioned the Humberto Vidal Shoe Shop Explosion, which happened on 21 Nov 1996, in the Rio Piedras section of San Juan in Puerto Rico. Folks in the shoe-store and elsewhere nearby had noticed the smell of gas for a few days before and complained to the San Juan Gas Company, a wholly owned subsidiary of Enron. That trail of ownership didn't bode well because Enron was notoriously cavalier about all aspects of their business except raking in money for it's senior management and share-holders.
ANNyway, SJGC sent a technician to check for the presence of gas and he, inadequately trained by lax management, switched on his machine when he stood in the cellar of the corner-shop shoe-store. As the machine was calibrated to detect differences in gas concentration, this action registered as zero. You're meant to switch it on in known clean air and walk on in to suspect areas. After the explosion, which killed 3 dozen people and injured scores more, Enron stoutly denied any responsibility, pointing at terrorists or sewer-gas (methane) as the culprits.
The building was blown to sticks propped up in a very unstable and dangerous condition but eventually the forensic investigators went in to determine the cause. A key bit of evidence was an interior pipe that had clearly been blown upwards. That indicted propane, heavier than air, which pools in the bottom of confined spaces rather than methane which accumulates from the ceiling down. The lawyers then moved in and over the next 6 years squeezed $20 million out of the parent company, doubtless hanging on to a large portion of that for their troubles. The municipality's response was to rip out all the gas pipes! That doesn't seem particularly sensible or scientific.