The inner walls of a typical home are constructed of sheetrock, wood or plaster, all of which are highly susceptible to the effects of mould contamination. If you do find signs of mould on your walls, you can use chlorine bleach to kill the active spores. Chlorine bleach contains strong mould-fighting properties, but can also bleach or damage your walls if not diluted and used with the proper precautions.
Pour 1 tbsp chlorine bleach into a spray bottle and dilute with 1/2 qt. warm water. Although you can use oxygen bleach to fight mould, a University of Missouri Extension report recommends chlorine bleach for best results against mould. Additionally, it is essential that you dilute your bleach with water in order to fight mould without bleaching your walls.
Mist your diluted bleach onto a soft cloth or sponge. If mould covers a large area of your wall, you may spray it onto a paint roller instead. Hold the sprayer a few inches away from the cloth (or other surface) while spraying, and allow only enough liquid to dampen (but not saturate) the cloth. If you soak your walls, you will only exacerbate the wet conditions that allowed mould spores to thrive in the first place.
Wipe down your wall using your cloth, sponge or roller. Make sure to wipe down any area where mould appears, as well as the surrounding areas. Even if a particular area seems unaffected, it may still have microscopic mould spores, especially if active mould exists nearby.
Remove the bleach from your wall after about 15 minutes. To rinse away the bleach, you may use lightly dampened paper towels, a dampened sponge or cloth. Once again, take care not to saturate your walls with excess liquid. You want to remove the bleaching agent, but not create additional moisture.
Dry your walls. Even if the bleach succeeded in killing all active mould spores, mould may still regenerate if you allow your walls to remain moist. Place a dehumidifier nearby to eliminate moisture from the surface of the walls, or turn on your air conditioner while running fans. You may also use a space heater.
If you notice mould covering a large portion of one wall or multiple walls and you cannot identify the source, contact a mould removal specialist. You may have leaky plumbing or an insulation problem that requires immediate attention.