Last spring, Michael Hammond, 36, and his wife, Sharon, discovered an unwelcome guest in their two-bedroom basement apartment in Silver Spring.

“We noticed the windows would have condensation on them when we came home in the evening, and we couldn’t explain it,” says Hammond, a muralist and painter. “And after a while it started to smell.”

They spent $200 on a dehumidifier, and had to empty its two-and-a-half-gallon tank twice a day. Their bathroom wall started crumbling. Their carpet was wet and brown. “We peeled back the carpet next to the bathroom and it was just black underneath,” he says.

“All the puzzle pieces started fitting together, and we figured it had to be mold,” Hammond says.

Mold is a form of fungus that thrives indoors and out. It grows best in warm, damp and humid environments. That means those April showers don’t just bring May flowers — they bring mold to area apartments, too.

Nelson Barnes Jr., an industrial hygienist and a certified mold remediator who owns Maryland Environmental Systems & Solutions (410-787-1400), says mold growth in apartments has to do with poor air supply.

Your apartment should have vents — often located in the hallway or bedroom — that constantly circulate air. Poor ventilation or reduced air flow through these vents can lead to mold growth, Barnes says.

He recommends turning on ceiling fans, which, when used with an air-conditioner, can make it more difficult for mold to grow.

If you’re worried you might live in a mold-friendly pad, go to a hardware store and buy a $15-$20 hygrometer to measure the temperature and relative humidity. Mold and bacteria grow in apartments that have humidity above 60 percent and dust, Barnes says.

Take a good whiff, too. “If there is a musty smell, or if the place smells like something out of the ordinary, that is the time for you to say, ‘Listen, there’s something going on here,’ ” he says.

If you discover mold in your apartment, ask the management to send a mold assessor like Barnes as soon as possible.

Unfortunately, identifying the mold is only half the battle. Barnes confirmed there was mold in Hammond’s apartment, but the landlord refused to cover the costs of repairs and mold removal. So Hammond and his wife had to move out.

If you’re dealing with a similarly difficult landlord, put everything in writing, says Beth Harrison, a supervising attorney at the D.C. Legal Aid Society. That way groups like Legal Aid may be able to help you.

If your landlord or property manager offers to fix the problem, make sure they hire a team that’s certified in mold remediation. That way you’ll know they’re removing the mold, not just covering it up.

You can avoid a future moldy situation by keeping an eye out for it while apartment hunting. Check each unit you look at for a ventilation fan in the bathroom and an exhaust fan in the kitchen — and make sure they work. Hammond found out too late that neither fan in his unit functioned.

Check for water stains on the walls, bubbles under the drywall, and rust and discoloration in the bathroom and kitchen. “Those things raise flags,” Barnes says.

And be sure to ask about it. “There’s nothing wrong with asking the management: … ‘Is there any history of microbial growth or mold?’ ” Barnes says.

Mold Debate Grows in D.C.

Pending legislation in the D.C. Council may give renters in the District new legal recourses to fix mold in apartments.

Currently, the D.C. housing code does not list mold as a housing code violation.

If a leaking roof leads to mold growth in an apartment, the D.C. Department of Consumer and Regulatory Affairs can only cite the landlord for the leak, but not for mold itself, explains Beth Harrison, supervising attorney at the Legal Aid Society of the District of Columbia.

So the Legal Aid Society, which defends low-income tenants in D.C., has worked with D.C. Council member Mary Cheh’s office to develop legislation that would include mold as a housing code violation. The D.C. Council unanimously passed the bill upon first reading in April.

The pending legislation requires the D.C. Department of the Environment to set a threshold mold amount, above which professional help is necessary. It requires landlords to disclose any mold above the threshold in the past three years that wasn’t fixed.

It also creates licensing/certification standards for mold remediators and assessors. And it requires a landlord to inspect for mold within seven days and to remedy the situation within 30 days. If not, the tenant can be awarded damages.

But there’s still a ways to go. The legislation has to pass a second D.C. Council reading, as well as gain the mayor’s signature and congressional approval before being formally enacted.

It also faces opposition from the Apartment and Office Building Association, which represents landlords.

However, Harrison is optimistic that she’ll have a stronger law to help protect her clients very soon. That first unanimous backing by the D.C. Council is “a good sign,” she says.

This article was corrected to include the role that D.C. Council member Mary Cheh’s office played in developing legislation to include mold as a housing-code violation.