Murrieta firefighter/paramedics suited up and descended underground via a manhole last week to practice their rescue techniques.
The Murrieta Fire Department conducts the drill, known as a confined space rescue, annually to ensure they are certified to handle similar real-life incidents.
Crews of 15 took turns undergoing the training that was set up at the west end of Vineyard Parkway, off Washington Avenue.
The drill begins when a dispatcher sends out an alert that two water department employees are stuck underground in a vault, with one person unconscious.
Firefighter/paramedics must practice their response, which for some includes wearing an oxygen mask while being lowered 12 to 15 feet underground by a pully for up to 30 minutes.
The vault, which leads to a main water pipe, must be checked for fumes before crews make entry, according to Murrieta fire Battalion Chief Steve Kean.
"We have a continuous supply of oxygen," Kean said.
Ventilators are also used to ensure a safe flow of air into and out of the vault, he said.
The firefighters must return above ground with the patients, in this case mannequins.
Others play different roles, such as handling radio communications while the below-ground personnel give status updates.
Pechanga Fire Department Urban Search and Rescue unit also participated in this year's drill, which was performed in conjunction with the Rancho California Water District.