The fire department deemed the area safe just before 10:40 a.m.
Volunteers must wear PPE and undergo a health and wellness check before each shift.
Prince George's County's technical rescue team responded to the scene Thursday morning.
Tiffany Green is also one of just a handful of black women to hold the position in the U.S.
The students are on call from 3 p.m. to 7 a.m. on workdays.