Sealed or Unsealed
Before using a steam cleaner on a wood floor, first determine whether the surface is sealed or unsealed. Sealed hardwood floors are treated with polyurethane or some other type of protective finish. Unselaed floors are typically found in older homes, and it is not safe to use a steam cleaner on these surfaces.
Damage to Floors
According to a review of steam mops on consumersearch.com, steam cleaners that have only one hole to release steam tend to leave floors overly wet. This is problematic because standing water and wood floors do not mix. The water can cause the flooring to warp, or over time, loosen. Carefully research models and note the design of the steam head before purchasing. Steam mops can also cause damage to wood floors because some models' instructions call to hold the unit in place for up to 15 seconds in order to sanitize the surface. Holding a steam mop in one area for that length of time can cause damage on wood floors.
Use a dust mop to keep wood floors clean. Clean the surface frequently with the mop. It has a soft surface that will not cause any damage to wood floors. Follow up by cleaning with a damp, not wet, mop. Dip the mop in water and thoroughly ring out twice before applying it to the floor.
Steam cleaners do safely clean tile, vinyl and laminate floors, when used correctly. Under the right conditions outlined above, sealed hardwood floors can be steam cleaned.