Daily care of concrete floors involves sweeping or mopping. Cleaners can use a commercial walk behind scrubber with mild detergents to pick up dirt and debris. Waxing is not necessary, so custodians require no additional training and this saves a step in the cleaning process. Maintenance staff should avoid using heavy-duty cleaners, acids and other chemicals on concrete floors since they may eat away at the finish. Also, because polished concrete is naturally porous, it is more prone to staining than other types of hard surface flooring finishes. To prevent discolouration, custodians should clean up spills as soon as possible to prevent them from penetrating the concrete.