If it is mold that is undetected, place bicarbonate of soda in containers in the suspect places. Half a teaspoon of oil of clove in a litre of water will kill mold spoors. Bleach does not kill them - they always come back if you use bleach. Spray onto the mould and wipe off after a few minutes. It will have a strange smell as well but it soon goes away. All the best with your problem.