starts an explosion and walks through it

“Heh. It looks like these containers held flour, but this nice windless night might be
making this a very dangerous situation.”
Kamijou looked questioningly in the direction of the voice.
“There are stories of explosions in mines, right? Those don’t happen because someone
didn’t use their explosives properly.” The voice sounded like it was grinning and
enjoying itself. “They were caused by the fine dust from the stones filling the air in the
mine. A lot like now.”
Kamijou jumped out of shock.
He figured out what Accelerator was trying to do, so he moved his battered body in an
attempt to get out of there.
“If there is powder floating in the air, it can be ignited. The combustion rate of oxygen is
ridiculously fast, so it seems all the air in the place becomes one giant bomb.”
Kamijou was no longer listening.
He was merely running as fast as he could without looking aside.
He had turned his back on Accelerator and was trying to escape that giant space filled
with that powder.
He ran and ran and continued to run.
Accelerator’s voice then pierced into Kamijou’s back.
“Surely you’ve at least heard of a dust explosion.”
Immediately afterwards, all sound was blown away.
The area with a 30 meter radius in which the flour had been scattered became a giant
bomb. The entire area became wrapped in flames and heat as if gasoline vaporized into
the air had been ignited.
Kamijou had just barely managed to escape the curtain of flour when it happened.
The shock wave struck his back and knocked him down to the gravel, but he managed to
avoid being enveloped in the flames themselves.
However, a dust explosion was different from a normal explosion because it used the
oxygen in the air as fuel. The explosion instantly stole all the oxygen in the area which
lowered the air pressure dramatically.

Fortunately, it had occurred outside rather than in a sealed area, so a vacuum was not
created. But the sudden change in air pressure internally squeezed on his organs to the
very limit. If it had actually been a vacuum, his body would likely have burst open from
the inside.
“Gah...Ahh...!”
Kamijou moved his battered body and just barely managed to stand up as the sea of
flames lit the switchyard up as if it were the middle of the day. He turned around toward
the pile of containers he had fled from.
Accelerator was walking there.
He was calmly walking through the crimson purgatory he himself had created.
“God damn it. I’m sure you just experienced it yourself, but the lack of oxygen was tough
on me, too. Fuck, I thought I was gonna die. You should be glad. I think you’re the first
in the world to make me, Accelerator, think he was gonna die.”
His voice was light, like he was just having a casual conversation.

- Toaru Majutsu no Index Volume 3, Chapter 4 Part 6