@MongoLloyd said:

A more dramatic and quick way to illustrate the incident but pretty silly either way because nope.

Nope it never happened? or Nope that would suck?

Nope, it never happened because it can't happen. Drain traps exist to prevent sewer fumes from backing up into a residence. And the actual accounts given of the event make no mention of the gas entering homes through drains.

But I understand that portraying it that way was easier.

@MongoLloyd said:

Nope, it never happened because it can't happen. Drain traps exist to prevent sewer fumes from backing up into a residence. And the actual accounts given of the event make no mention of the gas entering homes through drains.

But I understand that portraying it that way was easier.

While that maybe true you have to remember you're talking about Colombia here and not the United States.

I considered that, but still.

And, what actually happened:

"... that night four members of the Cali cartel tried feeding the gas down hoses into the sewer system of the city. But they misjudged the operation and the toxic gas soon started backing up out of the manhole, growing into a vapor cloud. The men quickly fled the scene but the gas spread throughout the neighborhood."

Chlorine gas is 2 1/2 times heavier than air so if no wind, it'll just hang around which is what it sounds like it did. That said, I don't see how it's possible a heavier than air gas made it's way UP through sink drains of residences.