Ventilate the basement as much as possible. Open all the windows and doors to the room, and place an electric fan nearby to help with circulation.
Sweep any loose dirt or debris from the floor to create a clear workspace. Follow up with a mop soaked in hot water and mild floor detergent to remove grease and grime.
Protect your hands against alkaline burns with a pair of solvent-resistant gloves. Follow the manufacturer's instructions for proper mixing and preparation of the paint stripper.
Apply the paint thinner using a paint roller, paint brush or aerosol can depending on the particular application type. Work with manageable areas of the floor to prevent walking on coated sections.
Refer to the product label for an appropriate wait time before proceeding to remove the paint. Use a long-handled scraper or wire brush to carefully loosen the dissolving paint; the necessary amount of pressure and time required for complete removal varies depending on how long the basement floor has been painted.
Scrub the more stubborn areas with a scouring pad or steel wool for a thorough removal of the paint. Mop the entire floor with the soap solution again to rinse the loose paint and stripper. Allow the concrete to air dry for 24 hours after cleaning before applying a new coat of paint.