To effectively mitigate the risk of mold or fungus, what should be applied to wood surfaces?

Applying wood bleach to wood surfaces is an effective measure for mitigating the risk of mold or fungus. Wood bleach typically contains chemicals designed to kill mold spores and prevent their growth, making it suitable for treatment when dealing with existing mold or as a preventive step in environments prone to moisture and damp conditions.

In addition to its mold-fighting properties, wood bleach can also lighten the wood's color, which may be beneficial if the wood has been discolored due to mold or if a uniform appearance is desired. It penetrates deep into the wood fibers, addressing potential fungal issues at their source.

The other options do not possess the same mold-preventive properties. Regular paint may provide a barrier to moisture but does not specifically target mold prevention. Oil varnish can seal wood but is not effective against mold growth. Wood stain typically adds color but does not have protective functions against mold or fungus either. Hence, using wood bleach is the most suitable method for effectively combating mold and fungus on wood surfaces.