A small room in the basement houses the furnance, electric water heater, water well pump and a crock in the floor with water which is pumped out a couple times daily. This room has been a bit humid as the rest of the basement. Black areas have appeared on the cinder block walls. With a finder wipe a black mark appears on the finger. I have sprayed it with bleach but does not disappear. To scrub it wet seems to smear it. Though the bleach runs onto a rag and is slightly discolored black. Is this a mold? The room seems to have a stuffy, stale smell. Any thoughts??

ballengerb1

Sounds like mold to me. You need to increase the evtilation in this room and reclean with a stronger bleach solution. You can try swimming pool chorline but there must be very good ventilation, there is a danger of injury to yourself. You can also buy a commercial mildwecide at most home centers.