The problem began at about 4 a.m. at the police communications center at Nevin Avenue and 27th Street, across from City Hall, police Sgt. Nicole Abetkov said.
She said that when employees noticed the fumes, firefighters were called in.
"The fire department went over there and decided to evacuate the buildings," Abetkov said.
The situation has since been resolved, and workers were allowed to re-enter the dispatch center around 8 a.m., Abetkov said.
During the closure, non-emergency and radio calls were being handled by dispatchers using one of the Police Department's command vans, Abetkov said.
Emergency calls went directly to the Contra Costa County Sheriff's Office, which is relayed dispatch information to Richmond police, Abetkov said.
"When we go offline, all our 911 calls go through the county," she said.
She said the Richmond Police Department also dispatches for El Cerrito, San Pablo and Kensington, so emergency calls from those cities also went through the sheriff's office this morning.
Abetkov said residents calling police did not have to do anything differently; the calls just went through a different route.
"We have plans to deal with stuff like this, and it's being dealt with," the sergeant said.