Flames bursting out of Air Products chemical facility shook buildings and residents at least five miles away from it.
"You heard the boom and then you felt like a wave, a pressure... a force. It just hit you all around you and moving you slanting you back," said Evan Rosales.
Rosale's catering business is a 10-minute drive from the plant and describes the flames as 50 feet high. Rosales says his first thought was to save his workers.
"I went outside and I told my workers to run to the back," said Rosales.
At least 4 workers at the Air Products plant located on 1515 Norman Avenue were on site during the explosion.
Santa Clara Fire arrived on scene at 4:30 pm and all signs point to a leak.
"The tanker truck was in the process of being fueled and it began to leak and there was a large hissing noise. The workers on site tried attempted to shut down the valve of the line that was fueling one of the trucks," said Battalion Chief for Santa Clara Fire Dept., Drew Miller.
It took firefighters an hour and at least three aerial master streams to put out the fire. The biggest challenge? Hydrogen is invisible.
"They were also using thermal imaging cameras from different vantage points to make sure that the hydrogen wasn't burning even after it appeared that it was shut down," said Miller.
Businesses around the plant were evacuated and a two-block radius shelter in place for several hours was ordered by firefighters.
"I was watching to see if there was another explosion so I would start running myself. That's how scared I was," said Rosales.
No injuries were reported. Santa Clara fire said they're investigating.