Phyllis Liu was released from Santa Rosa Memorial Hospital Wednesday afternoon, hospital spokeswoman Katy Hillenmeyer said.
Liu, 61, suffered first- and second-degree burns to 10-15 percent of her body during the fire at Alfred F. Biella Elementary School, located at 2140 Jennings Ave., Santa Rosa Fire Department Chief Mark Basque said.
School Principal Winnie Hogoboom said the accident happened around 10:15 a.m. No children were in the classroom at the time.
A nearby physical education teacher saw what was happening and rushed over to put out the flames, Hogoboom said.
Firefighters were called and the school was evacuated. Students stood in the rain while the situation was investigated, Hogoboom said.
Basque said the wax had apparently overheated and ignited. The volunteer was burned while removing a pot of burning wax from the classroom, he said.
The flash fire caused minor damage to the classroom, Basque said.