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NEW YORK (CNN/Money) - Many people, cozily ensconced in their favorite easy chair, take comfort in the feeling of safety and security their home provides.

"It's a dangerous world out there," they think. Well, it can get pretty dangerous in your home sweet home, too.

Here are just some of the potential perils lurking: Poisonous lead dust, toxic molds, radon, all sorts of allergens, chemicals vapors, and carbon monoxide.

Americans spend most of their time indoors. But concentrations of pollutants often exceed those found in the outside world. Exposure to some of those dangers can contribute to a host of health problems.

Some 20 million Americans suffer from asthma, for example, and another 50 million have allergies. Roughly 10 million suffer from both, according to Mike Tringale, director of marketing and communication for the Asthma and Allergy Foundation.

"Pet hair, mold spores, cockroach excretions, and dust mites are just a few of the allergens that can trigger full-blown asthma attacks," says Tringale.

For people who are especially sensitive, a healthy home -- built or retrofitted with low- or non-toxic materials and complete air-cleaning and ventilation systems -- is a necessity.

Dampness is the biggest threat to a home's health, according to Brian Gumm of the Alliance for Healthy Homes.

"Many other problems trace back to excessive moisture," he says. It can cause lead paint to flake and peel, facilitates cockroach infestations, and encourages mold growth.

Mold invades households via air-borne spores and on clothing and pets. The fungi gain footholds where leaks or condensation proliferate. Many building and decorating materials, such as sheet rock paper backing, ceiling tiles, insulation, carpet, upholstery, and wallpaper may nurture fungal growth. Molds also grow around standing water.

The worst molds can kill outright. A few years ago, nine infant deaths in Cleveland were attributed to the fungus stachybotrys atra.

It can also plague people with allergies or those whose immune system is compromised or have an underlying lung disease.

When energy prices soared in the late 1990s, homeowners tried to increase their house's energy efficiency by making homes more air-tight. A tighter home, however, can also mean less air exchange. Problem areas, such as bathrooms and basements, don't dry out as quickly and foul air hangs around; molds and germs can multiply and poisons can concentrate.

David Wluka, a real estate broker in Sharon, Mass., said he was the importing agent for Swedish panelized housing systems some years ago. The houses were shipped in modules and assembled on site, but they didn't meet federal code.

"They were too tight," he says. "We had to add an air exchanger."

Excessive moisture is especially acute in high humidity locations, and can be hard to solve. "Fixes don't work in some places," says Rebecca Morley, executive director for the National Center for Healthy Housing. "In Florida, vinyl wallpaper is a disaster. It serves as a barrier and warm air condenses on the inside of the walls."

Hypersensitive homeowners may need to take extra steps to protect themselves. They often shun modern building materials such as plywood, paints, and stains because the adhesives or dryers in them can break down into chemical vapors. They also limit their use of carpeting and upholstery, employ only user friendly cleaners, and try to eliminate pests through non-toxic means.

Even people not directly threatened by indoor perils may want to improve the overall quality of the living space. There are several things they can try.

• Ventilation: Systems that exchange flush stale air several times a day and replace it with filtered fresh air not only remove pollutants but reduce excessive moisture. In cold climates energy efficiency can be maintained by using a heat exchange system in which incoming air is warmed by out-flowing air.
• Spot ventilation: Venting kitchen fumes and moist bathroom air is very important. Gas ranges produce carbon monoxide and release it directly into the atmosphere, especially if the unit is not working properly.
• Non-toxic materials. Use natural stones and woods, ceramic tiles and low shag rugs, stainless steel countertops.
• Keep it clean: Pet dander and dust is especially dangerous for asthma sufferers.
• Maintain your alarms: Smoke, carbon monoxide, and radon detectors should be periodically checked to make sure they're still functioning.
• Use non-toxic cleaners: Cleaning agents and pesticides (as well as upholstery fabrics and carpet materials) may emit volatile organic compounds (VOCs), including formaldehyde. The chemicals can cause a wide range of respiratory and neurological conditions including cancer.

Click here for a sample of healthy home for sale around the country.

Click here for information on hazards that you need to disclose to potential home buyers when you sell your home.