Q.  Can mosquitoes develop indoors? I thought they needed water, but we keep getting bitten in our house even though all the windows are closed and the AC is on. We don’t have a real mosquito problem outside, just inside! A. Yes, mosquito larvae do develop in standing water, and the standing water needs to contain some kind of organic material for the larvae to feed on. For that reason, although mosquitoes can get into a building, they rarely breed and develop inside a building. But it can happen in unusual circumstances. Several years ago we dealt with a mosquito problem at an old apartment property. Residents of building 110 were getting bitten by mosquitoes outside the building and also inside the building. We couldn’t find any standing water on the grounds and residents of adjacent buildings had no mosquito complaints. The 50-year old brick apartment buildings had attached boiler rooms that were no longer in use and had been blocked off. This is where we found our breeding mosquitoes.

In building 110, the huge boiler room was 100 by 50 feet and 30 feet high and most of the boiler room was below ground level. We discovered that an underground spring had been slowly feeding water, now 2 to 3 feet deep, into the boiler room. One small window near the ceiling allowed mosquitoes and debris to get into the water which was teeming with mosquito larvae and pupae. The emerging adult mosquitoes then found their way out of the boiler room either through the window or up into the connecting apartment building. The building’s residents were literally sitting on top of an indoor mosquito swimming pool. In your case, however, you need to think about unseen areas of standing water that could be in your home. In my own home, I once had mosquitoes breeding inside a potted plant container. The plastic pot with drain holes had been placed inside a prettier ceramic container. This plant was the last stop in my search for the cause of our indoor mosquito bites. When I pulled the plastic pot out, there was about an inch of dirty water in the bottom of the ceramic pot—and plenty of mosquito larvae and pupae!

Somehow a single female Asian tiger mosquito found her way into the house, probably fed on one of us, then managed to find that single source of standing water in which to lay her eggs!air handling unit measurement Other possible indoor breeding sites for mosquitoes are unused floor drains such as in laundry rooms or basements, shower drains in bathrooms that are rarely or never used, or sump pump pits. tape for ac unitAlso check drip pans in dehumidifiers or under refrigerators or AC units. base for outdoor ac unitEven a half-full bucket of dirty water in the laundry room or a pet water dish left in the basement can breed mosquitoes if the right circumstances exist.As we’ve noted before, an entire apartment building can become “sick” from mold in an improperly maintained central HVAC—causing respiratory problems, headaches and rashes in some people.

But mold can also be served up a la carte, one apartment at a time. Although both new and old apartments are at risk, experts say mold problems are increasingly cropping up in new-construction apartments. Sealed up more tightly, "they don't breathe as much, and if there is some kind of leak or water damage, mold can grow," says Jeff Gross, a water damage and mold remediator at Maxon's Restorations, a Manhattan-based property damage restoration company.   Top 3 sources of moldGross gave us the scoop on the top three mold-producing scenarios in new and old NYC apartments, as well as the ballpark costs for dealing with each: Culprit #1: Leaks from another apartmentPipe breaks and water overflows can soak your ceiling and walls from above, or seep into your floors and walls from the side. The most common offender: Plastic water supply lines to sinks and toilets.  (Tip: Copper almost never leaks, says Gross.)Treatment:  If, for example, your upstairs neighbor's toilet or shower overflows into one room of your apartment, your ceiling and walls would be affected.  

Professional water remediation--simply drying out area behind the wall to prevent mold--costs about $1,200-$4,000. That process takes about 3-10 days and includes sucking up the standing water, making holes in the wall to ventilate the wall cavities, possibly pulling down a light fixture to get air into the ceiling, cleaning and treating all surfaces with an antimicrobial agent, and setting up drying equipment.If mold is present and the affected area exceeds 10 square feet, the NYC Department of Health Guidelines on Assessment and Remediation of Fungi in Indoor Environments requires a full-scale mold remediation by a trained and qualified professional like Gross. (Note: Unlike lead and asbestos, there is no licensing requirement for mold remediation.) Expect the pricetag to go up to $6,000-$10,000 for a full mold remediation.  With many insurance policies carrying mold exclusion these days, you may wind up paying for all of this yourself. Culprit #2: Clogged PTAC UnitsThese all-in-one heating-and-cooling units, located radiator-style against the wall, are a huge blind spot for NYC apartment owners, who tend not to realize that PTAC units require twice yearly maintenance and that as the owner of the apartment, it’s their responsibility, says Gross.“

The most common occurrence with the PTAC units is that the filter is not replaced often enough,” says Gross.  “Dust collects on the filter and on the coils, and through condensation it drips into the condensate pan and clogs the drain. Then the condensate pan overflows and leaks under the floor. And also people forget to clean them after doing renovation where there’s a lot of dust.”Unfortunately, dripping PTAC  units tend to cause mold more often than other types of leaks, says Gross, because they leak so slowly into the floor that it’s not noticed until a large section of flooring shows damage. Nearby sheet rock can also be implicated as it wicks up the moisture from the floor.Treatment:  If you are lucky to catch it soon after it begins to leak, cleanup can simply involve removing a few floor tiles, removing the base molding and drilling a hole to dry the wall cavity. This can run $500-800 and require minimal repairs. When mold is present, situations like these nearly always require a full-scale mold remediation as they tend to exceed the Department of Health’s 10-square-feet rule.

Remediation typically involves ripping out a few square feet of floor, sheetrock and base molding to get rid of mold. Average cost is around $4,000, plus the cost for a contractor to come in and repair the area afterward.Culprit #3: Broken washing machine hose“We get a lot of these,” says Gross. “When you buy a washing machine, even the fancy ones, they install them with inexpensive rubber hoses—those are the ones that break, as opposed to the $40 stainless-steel-wrapped hoses you can buy at Home Depot that almost never leak.” Treatment: “If we come in right away after the leak is caught, we’ll vent the wall cavities, pull the base moldings off, drill holes and get air movement into the wall cavities to dry them," says Gross. "If there’s a wood floor we may try to dry that too unless it’s already showing evidence of buckling and cupping.”  For one room, he says, the cost is  around $1,200-$5,000. If mold has already set in, a full scale remediation would entail removing the flooring and base moldings, cutting the sheetrock walls up two feet around the perimeter of the room, then treating as described below.

Cost: $5,000-$8,000.How to tell whether you have mold in your apartment So how do you know if you have a mold problem? It’s not always obvious, says Gross.Water damage: You'll probably notice water damage and staining before you notice any signs of mold, because mold tends to grow faster inside than on the surface. That’s why it’s important to address any moisture problems quickly.Odor:   One of the first signs that mold might be present is a wet, musty smell or the smell of moldy, wet building materials. These indicate a moisture problem that can lead to mold; it doesn't necessarily mean you have mold.Spots:  Black, gray, green or brown spotting.  (Note: This is similar to what you see on your bathroom surfaces—a.k.a. mildew. Those tend to be surface stains from moisture and soap-residue buildup and can be easily cleaned up with standard bathroom cleansers)Health problems:  Respiratory reactions including asthma are most common, though mold sensitivity can also cause headaches and skin rashes. 

Some people have symptoms immediately; for others, it develops over time.  Note that not all types of mold cause health problems; to identify which type you have, an industrial hygienist will need to collect a sample for testing.  Anatomy of a full-scale mold remediationFull-scale mold remediations in New York City apartments typically cost around $4,000-$12,000, says Gross.  Unless your insurance excludes mold, which many policies do, it will be covered if caused by a ‘covered event’ like a pipe break or overflow from next door. (For more information on insurance coverage of mold claims, click here.)To understand why your handyman isn’t perhaps the best person for the job of removing mold, here’s Gross’s description of what goes into a full-scale mold remediation: Containment of the work area: “Mold is a living organism and when you disturb it kicks off spores into the air, so we seal off the work area by building a tent of poly sheeting around it to prevent cross contamination.”

Negative pressure of the work area:  “We exhaust the work area through HEPA filtration usually to the outdoors. That basically puts the area in a vacuum—the negative pressure prevents mold spores from migrating out of the work area into the rest of the apartment while we’re working.”Removal of contaminated materials: “It’s more of a surgical removal than a demolition. We don’t use sledgehammers—we use knives and spray bottles to wet down the material. The debris we create is bagged in poly bags taped shut and the exterior has to be vacuumed to prevent cross-contamination. Surfaces that can’t be removed, like a concrete slab, have to be cleaned and if there is evidence of contamination, have to be encapsulated in an antimicrobial sealant, like a primer.”Cleaning: “We assume the entire work area is now contaminated.  All surfaces must be cleaned in a three-step process--HEPA vacuuming, damp wipe and HEPA vacuuming--sometimes called the HEPA sandwich.  We also scrub the air—air is filtered over and over again through HEPA filtration, at least four air exchanges per hour for 12-24 hours.”