Ever since we found out that older homes in Hawaii have fireplaces primarily to keep the house dry, rather than warm, well, it’s been raining pretty often. Things are damp. And when environments are warm and damp, your whole house becomes a prospective petri dish.

"Mold!" said cleaning expert Mark Johnson of Aloha Restoration. "When things get wet, you have three to five days before mold starts to grow. Some types of mold are dangerous, particularly to children and elders."

"You have about 72 hours, roughly, before the first mold appears," explained Demetrius Santana of DAJ Carpet Cleaning and Restoration. "It’s very small, and you might not be able to see it at first, so you have to mitigate the flooded areas and apply heat and ventilation."

"The first step is determining the water source if you’re flooding," said Santana, noting there are three general flood points — from a sanitary source, such as pipes within the home; water that is contaminated enough to possibly cause sickness; and water that is grossly contaminated, such as sewer overflows. "If the leak is from plumbing, pretty much everything is salvageable, if you get to it in time. Water from a stream or ground is dirty, and nothing can be saved."

Furniture, because it’s easily ventilated and cleaned, said Santana, can often be saved. Homes with drywall plaster, on the other hand, can trap moisture within the wall, creating explosive mold growth.

"You’ll see growth on the surface of walls, green, brown and black, circular patterns and spotty," said Darren Kaneshiro of MD Cleaning and Restoration. "And what’s going on inside the wall is worse.

"A homeowner can do small things themselves, like drying out throw rugs. You just hang them up to ventilate and get good airflow," said Kaneshiro. "But wall-to-wall carpeting — to put it bluntly, usually, it has to go. It’s so thick and traps so much water underneath.

"The paint finish on a wall can make a difference too. A high-gloss finish traps water inside. One thing you can do is pull the baseboard off. It opens up the unfinished parts of the drywall and lets it dry inside. You should leave it off at least a couple of weeks."

Some houses have small floods due to heavy rain — that’s where professional outfits like Aloha Restoration, MD and DAJ come in handy — and some have highly localized water problems, like a drip-drip leak from the back of the toilet.

Kaneshiro estimated 90 percent of freshwater flooding comes from the same source: "the water supply line behind the toilet," he said. "The plastic connections become brittle over time and start to drip. They’re easy to replace and should be done every couple of years. Finger-tighten the connections — don’t use tools — because you can overstress the plastic."

Another primary flooding source is the supply lines to washing machines, because the machines vibrate and rattle the lines.

Flooding doesn’t happen often. What we deal with every day in Hawaii homes comes down to humidity and ventilation.

Humidity is the percentage of water suspended in the air, and ventilation is the ability of air to pass freely. Basically, humidity below 25 percent is considered too dry, and anything above 50 percent is too damp. Humidity between 40 and 50 percent is considered ideal and comfortable. The Hawaii average, however, hovers at around 65 percent.

We get away with the high, year-round humidity in Hawaii thanks to the moving air caused by the trade- winds, and Hawaii homes are famously well ventilated to allow moving air through the structure, which helps wick moisture away.

If areas of your home are both damp and poorly ventilated, a dehumidifier might be helpful to cut down on mold and pest infestations. Just remember that the standing water created by the dehumidifier needs to be emptied out, otherwise it might leak or evaporate back into the room air.

"Air conditioners and dehumidifiers help, but if they lower the temperature in the room too much, they can work against you," said Kaneshiro.

You might try purchasing an inexpensive "hygrometer," a gadget that measures both temperature and relative humidity (they are amazingly cheap on eBay) and check the highs and lows at various locations around your house.

"Another thing to watch out for is if water has gotten inside your walls," said Johnson. "Many homes in Hawaii are single-wall, with the inside surface typically being just drywall. The space inside can get moldy, and it won’t be immediately apparent from the outside."

By the way, many homeowners’ insurance policies don’t cover flood damage. That’s usually not the case of water damage incurred within the home, particularly important for condo owners. Check your policy.