Engine 53 responded to the 300blk of S. Newtown Street Road to assist Newtown Square Fire Co. on the CO leak inside a nursing facility.  First arriving Co. 41 crews found high levels of Carbon Monoxide in the bldg and upgraded the assignment to bring additional manpower.  Crews evacuated the entire facility, were able to secure the source of the CO, and ventilated the building.  No injuries were reported and Engine 53 returned to Marple after approximately 90 minutes.