Firefighters responded to reports of a house fire at around 5:10 a.m. at 138 Marnell Ave.
They arrived to discover black smoke pouring out of the open front door and flames inside the home, officials said.
The occupants, a man, woman, and two young children, were wakened by a smoke alarm. They evacuated the home before firefighters arrived but responders found the man inside attempting to put out the fire.
With the aid of Central Fire Protection District, Santa Cruz firefighters put out the flames and discovered that the fire had started in an air purifier next to the wall.
The man was checked for smoke inhalation and minor injuries at the scene but he refused to be transported to the hospital, officials said.
Fire officials estimated the fire caused about $20,000 in damage, officials said.