A combination of high moisture levels and warm temperatures can make bathrooms common places to find black mold. Relative humidity levels in excess of 55% can support most types of fungus, but a bathroom that remains very damp and humid and reaches levels as high as 90% humidity or higher may run a higher risk of developing black mold.
Some of the most common circumstances in which black mold grows in bathrooms include water damage such as a broken supply line that goes undetected for a long period of time. Standing water is a common cause of black mold outbreaks.
The same cleanup measures apply whether the mold growing in your bathroom is in the genus Stachybotrys chartarum — black mold that may be toxic based on the subspecies — or any other species. Infestations involving toxigenic black mold call for professional mold remediation, as containment and expert remediation may be necessary to control the risk of exposure and spread of spores.
Assess the Severity of Bathroom Mold
A property owner can determine the severity of a bathroom mold infestation based on the type of mold and the extent of an infestation. In order to identify mold, it may be necessary to put on personal protective equipment such as gloves, goggles and a mask or respirator to gather samples for a home mold test kit that is submitted for lab analysis. For more reliable test results, arrange for expert mold inspection and testing. Any infestation of toxic black mold is more severe than mold problems involving species that are only allergenic.
It is also important to determine how many square feet are infested before starting mold cleanup. The United States Environmental Protection Agency categorizes the severity of fungus infestations based on the following size ranges:
Home bathrooms are more likely to experience minor to moderate mold infestations, but the presence of a toxic mold species increases the severity of these infestations. Moderate and major infestations may require limited containment, but most large and toxigenic mold infestations will require full containment.
Decide Which Cleaning Solution To Use
The mild acetic acid in distilled white vinegar with a 5% or 6% concentration is sufficient to kill the vast majority of mold species, including many types of black mold.
Approximately 80% of mold species can be eradicated through the use of vinegar. This natural treatment is more effective than chlorine bleach. Chlorine can disinfect moldy surfaces but cannot soak into porous materials, and the water in this solution may support growth under the surface.
Other effective cleaning solutions for porous and non-porous bathroom surfaces and fixtures include sodium borate or Borax, sodium bicarbonate or baking soda, and hydrogen peroxide. Whereas vinegar is an acid with a pH level of 2.5, Borax and baking soda are basic. Hydrogen peroxide is slightly acidic but is most useful for its bubbling action. A combination of baking soda and hydrogen peroxide can combine the power of fine, abrasive particles with bubbling action.
How to Clean Surface Mold in The Bathroom
Any effective antifungal treatment works on the surface of mold. Chlorine bleach is effective at killing mold on hard, non-porous surfaces, but is dangerous to use in combination with vinegar, as this produces toxic chlorine gas. If you are treating mold anywhere in your bathroom with vinegar, it is best to use this cleaning solution everywhere in a bathroom for single or repeat applications.
Baking soda and hydrogen peroxide also have a powerful surface cleaning action. While baking soda may abrade the surface of porous materials, these cleaning solutions do not penetrate deep enough into moldy drywall, grout or wood to eliminate the hyphae and mycelium that form the root structure of mold.
Mold Cleaning Tips for Porous Materials
Pour full-strength vinegar into a spray bottle designed to dispense cleaning solutions and spritz directly onto mold colonies. Give this treatment one hour to penetrate into porous materials such as grout or wood before removing surface growth with a scrubbing pad or brush.
A property owner may want to seek an expert opinion regarding whether cleaning is sufficient for porous materials or contents contaminated by black mold or whether trace growth could result in recontamination. When porous building materials such as drywall or insulation become completely contaminated with mold, it may be necessary to tear out and replace these materials. Rotten wood should also be disposed of and replaced near the end of remediation.
What To Do If Mold Returns
If an infestation of black mold returns to a bathroom, the conditions are still capable of supporting growth. Once visible mold has been cleaned, it may be necessary to assess the condition of porous building materials such as drywall, which may be causing recontamination.
Contaminated materials must be torn out and replaced. Low humidity and proper ventilation will remain crucial for discouraging new growth. Regularly scrub mold-prone surfaces with an antifungal solution such as diluted white vinegar. It may be helpful to run a dehumidifier to drop humidity levels to 50% or lower after bathing or showering. Restoring water damage in a timely manner prevents most black mold problems.
FAQs Regarding Bathroom Mold Remediation
Black mold growing in showers thrives on high moisture levels. Regular antifungal treatments and proper ventilation for fast drying are needed to keep mold from growing back after cleaning. Mold growing on grout requires the use of a cleaning solution that will sink into porous materials, such as white vinegar.
In general, the United States Environmental Protection Agency rates infestations that affect less than 10 square feet of a structure and involve non-toxic mold as minor mold damage. You may have moderate or more severe mold damage if a larger area is affected or an infestation involves a toxigenic species.
Black mold may or may not be toxigenic. Always wear PPE such as a mask, half-face or full-face respirator, goggles, and gloves when attempting mold removal. Call professionals for large black mold infestations, as partial or full containment may be necessary to limit exposure and keep spores from spreading.
Bathrooms combine moisture, sources of nourishment and warm temperatures, all of which have the potential to sustain many species of fungi. Black mold, or Stachybotrys chartarum, tends to grow in locations that are consistently damp, which may apply to a bathroom that is not properly ventilated, cleaned and dried between uses.
A bathroom that is slow to dry is prone to developing mold. Proper ventilation goes a long way. If fungus continues to form, apply a shower spray or vinegar cleaning solution every day or several times a week. A shower squeegee may also be helpful for the fight against mold.
Some subspecies of Stachybotrys chartarum are toxic. Even non-toxigenic black mold can still be allergenic and pose risks of irritation or more serious reactions to sensitive occupants and individuals with chronic respiratory conditions or compromised immune systems. Any black mold should be carefully removed and treated with antifungal or mildewcide.
Spray full-strength, distilled white vinegar or a solution of vinegar diluted in water onto your bathroom walls. Allow this treatment to sit for at least an hour before scrubbing with an abrasive pad or a brush that has firm bristles. Dispose of contaminated cleaning tools to keep an infestation from spreading.