Remember last week's deadly blast at a Chase Bank in Youngstown, Ohio?

Turns out the whole thing was caused by worker negligence:

A crew working in the basement area of an Ohio building intentionally cut a gas line not knowing it was pressurized before a deadly explosion this week, the National Transportation Safety Board said Friday.

The crew was "clear[ing] out piping and other outdated infrastructure and debris from the basement and vault area" in preparation for an infill project. The gas pipe that caused the explosion was "an apparently abandoned service line coming off the main."

Workers "smelled no gas before they started cutting the pipe" but they quickly realized the danger of the situation and ordered an evacuation of the building. The explosion happened six minutes later.

As an aside, here's a little science lesson.

You might be asking yourself right about now: "Why would the explosion take six minutes to occur after they cut the line?"

It's a great question! Here's a useful inquiry:

Q: I thought natural gas isn't really under much pressure or force. If cutting the line didn't immediately cause an explosion, why didn't they stuff something in the end of the open line until they could get to a valve?

A: [O]nce the line was cut they immediately set off the fire alarm and started evacuating the building. While the gas line is not under immense pressure, if the main line was cut and leaking out at 100% capacity it could have easily filled the space with a lot of gas. This is especially so if it was a larger commercial building that might be using medium to high pressure lines. The gas line was cut and leaking for about 6min which is a pretty long time if there is a major break in the gas line.

What happens after the area is flooded with gas? Well:

The line doesn't usually explode when you cut it. It shoots a plume of gas into the air and then something else typically causes the ignition. Light switch, open flame, outlet, static, etc

That's how you go from cut gas line to this:

The explosion was so powerful that it reached up to the 12th floor of the building:

This is why we need strict safety rules on job sites.

I'll leave you with a bit of history on the building:

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