The fire happened around 7:20 a.m. Monday at a storage facility in the 2100 block of 11th Street called "Overkillz Studio."
Police said the renter was hosting illegal parties in the space.
After the fire was put out firefighters found 3 tanks of nitrous oxide.
The gas commonly used by physicians to help numb patients can also be used to get "high."
Investigators said if the fire reached those tanks during a party the outcome could have been a lot more violent.
"With the fire the nitrous oxide inside the building it could've been a lot worse, then especially had all those substances been present this weekend, it could've ended quite differently. We're glad it didn't," said Rockford Police Sergeant Carla Redd.
The renter was arrested for possession of drug paraphanelia.
The building was condemned after it was discovered it did not have a working sprinkler system, water or heat.