If you have a tenant with mold sensitivities who alerts you to a mold problem, the appropriate response may not be obvious.

You may think that it’s your responsibility to clean it up, but many times, it’s not. It depends on the severity and cause of the problem.

On one hand, it’s impractical to mount an expensive remediation project for a problem that may exist more in imagination than reality. On the other hand, failure to respond to a genuinely hazardous condition could result in significant discomfort for a sensitive individual, and it could also result in a lawsuit.


Governing Laws on Mold Remediation

As of January 2016, there was no federal law setting permissible limits or tolerance standards on mold in residential building, and only six states — California, Indiana, Maryland, Virginia, New Jersey and Texas — had passed laws regulating mold levels in indoor environments.

While the other 50 states don’t specifically legislate mold, they do require the landlord to disclose potentially hazardous conditions at the time of rental, and they also require landlords to correct conditions that make a dwelling uninhabitable. Toxic mold is arguably one of those conditions.

Some municipalities have laws that clearly define the landlord’s responsibilities.

  • In San Francisco, property owners are required to maintain buildings “free of lead hazard and mold,” according to a circular published by the Department of Health.

The Good, the Bad and the Ugly

According to the Centers for Disease Control and Prevention, there may be as many as 300,000 varieties of mold on our planet, and many are benign. Some, such as Penicillium, are even beneficial.

Because they are virtually everywhere, however, it may be impossible to take a breath without inhaling some type of mold spore, and most people do so without consequence. Sensitive individuals, however, can experience respiratory irritation, aggravated asthma symptoms, headaches and other ailments, especially when certain strains are present. The two most problematic are:

  • Stachybotrys chartarum — Otherwise known as toxic black mold, this strain produces a mycotoxin which is responsible for the distress it causes. It grows in moist dark environments, such as in basements, damp framing and water-damaged drywall. It gets its name from its ponderously sinister color and heavy texture, both of which are warnings that it’s nothing to trifle with.
  • Aspergillus — Aspergillus is a family of molds, and only some of them produce mycotoxins. Probably more common than Stachybotrus, it grows in most of the same places. Lacking the threatening appearance or black mold, it may be even more dangerous, because it’s lighter and more easily airborne.

There is no guarantee that either of these species are growing in any particular mold colony, but testing for them would require detailed inspection with a microscope and is usually impractical. Consequently, any mold colony growing in a dark, wet place in a dwelling unit is suspect, and it’s difficult to claim that toxic strains are absent and that a particular colony is harmless.

Who Should Clean it Up?

It’s clear that any mold that results from a plumbing or structural leak should be addressed by the landlord as part of the repair. But should a landlord feel compelled to respond to a mold problem caused by unsanitary domestic habits? Probably not.

Landlords aren’t required to provide cleaning services, and to insist on doing so would constitute an invasion of privacy. For example, it would be reasonable to expect a tenant to clean up a mold colony growing in a corner in which he or she habitually throws damp towels.

Between these two extremes, however, are many gray areas. For example, mold often grows inside drains that habitually clog. A clogged drain is usually caused by what goes in the drain, not the drain itself. Or consider that mold may grow in a poorly ventilated crawl space, but the lack of ventilation may be due to piles of stored belongings.Here are some industry standards on the responsibility of mold remediation, but please know that each county, or Judge, might view this differently.