The propane bombs in the cafeteria were on timers set to detonate at 11:17 a.m., the time Eric had determined to be when the most number of students were in the cafeteria.
Eric had it down to a science. He determined that in the timespan of just 4 minutes, from 11:11 a.m. to 11:15 a.m., the student population would increase from roughly 300 to 500.
Eric and Dylan assembled and brought two 20 pound propane tank bombs into the cafeteria in duffel bags. They had cans of gasoline attached to them.
Something you need to know about their propane bombs before you read any further, is their construction and purpose.
Each propane tank was connected to a gas can and they used Visco for the fuse. (Cannon fuse). They used Westclox manual alarm clocks for timers. Yes, the timers had plastic hands. Plastic does not conduct electricity. But although most people think that this could have been the “faulty wiring” that made the timers ineffective, this is not so. They did not use the hands to complete the circuit, they used the bells. The way it would have worked would be for the alarm to go off forcing the bells to ring together, completing the circuit. The alarms failed to go off possibly due to being stuffed into duffel bags, or turned on their sides. Anything could have pushed the alarm buttons back in. Had the alarms gone off, they still would have failed to produce massive casualties. Here’s why.
The gas cans were attached to the propane (LPG) tanks to produce a BLEVE (Boiling Liquid Expanding Vapor Explosion). In order for this to happen, the propane tank MUST be heated. This is why the fuse was connected to the gas can. When there is enough heat next to a propane tank, the propane evaporates and rises to the top which creates more pressure. Then it eventually explodes.
Their plan was to have the fire from the gas cans heat up the tanks to their failing point when they would explode, and that would flush surviving students outside where they would pick them off at their will with guns.
But like I said before, even if the alarms had gone off, and the gas in the cans caught fire, there are more problems with this plan.
The sprinkler system would put out the fire before the propane tanks got hot enough to explode. How do I know this? It takes 8-30 minutes for a BLEVE to take place with a propane tank depending on all kinds of factors. The average time is 15 minutes for the industrial sized tanks. This is according to the NFPA. They are an authority on the subject… The smaller the tank, the less time it takes for it to fail. 20 Pound propane tanks contain 4.5 gallons and would take close to 5 minutes to heat up enough to reach the failing point.
Schools are trained to evacuate students in 90 seconds when the fire alarm goes off. Had it gone off at 11:17, the students would have fled within minutes. It isn’t likely that a cafeteria full of students would remain inside of the building while a fire burned next to them for even two minutes.
Eric and Dylan wanted to flush students out and shoot them as they ran. The students would not have been killed from a bomb blast had the propane tanks failed because it wouldn’t have taken them more than 5 minutes to evacuate. And in 5 minutes, the sprinklers would have put out the fires from the gas cans and they would have never exceeded their pressure limits.
The media likes to sensationalize everything by saying they could have killed 500+ students if their bombs were wired correctly. A 20 pound propane tank wired for a BLEVE couldn’t explode immediately and it would not have taken down the library on the second floor; however, it would have done minor structural damage. But kill students? The only way a BLEVE from two 20 pound propane tanks could have killed students is if they were in the direct path of the projectiles created by the sides of the tank as it exploded. It isn’t likely that anyone would have stayed in the cafeteria long enough to witness the tanks explode. The fire would have taken too long to heat them up. No one would have stayed to watch the fireworks as most people exit a building when there is a fire.
Did you know?
Eric and Dylan poorly constructed all of their bombs, including the cafeteria bombs.
Their cafeteria bombs were set up for a BLEVE which is a “boiling liquid, expanding vapor” explosion. There was no detonator of any kind. The attached gas cans were supposed to ignite a fire that would heat up the tanks, causing them to build pressure until they exploded.