Fill a bucket with water and enough dishwashing liquid to create suds. Scrub the surface of the fireplace with the soapy water using a stiff scrub brush.
Rinse the scrub brush in water and scrub the brick again to rinse off the soap. Let the fireplace air dry.
Put painter's tape on the wall along the edge of the fireplace. Lay plastic drop cloths on the floor along the fireplace.
Pour white interior paint into a paint tray. Dip a paint roller into the paint tray and roll it back and forth to coat the roller.
Roll the paint onto the fireplace, starting at the top and working down to the floor, then moving to the next section. Keep the layers thin and even.
Paint over any missed spots with the paint brush. Fill in any holes or low spots in the brick where the roller could not reach. Let the paint dry for 24 hours, then apply another coat if you need more coverage. Let the paint dry for 48 hours.