Firefighters arrived at Aramark Uniform Services on Shields and Clovis around 9:15 Tuesday morning.
Employees evacuated the building but two of them had to be treated for smoke inhalation.
Overhead sprinklers inside the business helped contain some of the fire damage.
But investigators say because of the large amounts of water the building will require an extensive overhaul. The cause of the fire is under investigation.
The company supplies industrial uniforms including work shirts and pants.