Although the air inside your home may not have the gray tinge of a smoggy city skyline, it can still contain invisible toxins and irritants that can lead to difficulty breathing, increased allergies, and other problems.

The simplest solution? Open a window. “Introduction of outdoor air is one important factor in promoting good air quality,” says an article on the website of the United States Environmental Protection Agency (EPA).

But when it’s too chilly to crack a window, it’s sometimes necessary to take bigger steps. Here are some preventative and maintenance measures homeowners can take to improve air quality throughout their homes.

HVAC Maintenance

Wayne Krasnow, the owner of Air Inc., in Branford, has suffered from asthma throughout his life. After attending trade school to study heating, ventilation, and air conditioning (HVAC) and learning the importance of maintaining indoor air quality, he made several changes to his own home and work spaces.

“I have a high-filtration system in my house,” said Krasnow. “In my company, the pleated filters are the only ones we’ll use. Those catch more dust than a regular filter and help people breathe a lot better.”

Also important is continual upkeep of home heating and cooling systems. “We make sure they’re running efficiently, which gives customers a better air quality and ensures safety for customers,” said Krasnow. “Maintaining their system also helps them save an average of 10 to 15 percent on their energy bill.”

The EPA says that keeping humidity levels between 30 and 60 percent can help prevent issues with mold. In addition to checking that bathrooms and dryers are properly vented, Krasnow recommends installing both central air conditioning and humidification systems.

“Air conditioning is a dehumidifier in the summer that takes the stickiness out of the air, as we saw with the heat waves this summer,” said Krasnow. “The humidification systems help people breathe better in winter, when the air is much more dry.”

Air-Duct Cleaning

A major part of keeping indoor air healthy is taking care of those hidden passages it circulates through. Krasnow recommends having your home’s air ducts cleaned every five years.

“It takes all the dust and dander out of the ductwork,” said Krasnow. “Anything that the return air sucks in goes through the ductwork and is blown back out into the air you breathe.”

Tricia Robinson of Branford was facing surgery to treat her continuous sinus infections. She and her husband, Steve, decided to explore other options to get rid of potential allergens. They hired Dependable Heating & Cooling of North Branford.

Although Tricia’s problem turned out not to be allergy related, she was shocked after seeing all the dust and other gunk that had been trapped in her ducts.

“When you saw what they took out,” she said, “it’s worthwhile.”

Go Green

A 1989 NASA study showed that houseplants can help remove toxins such as benzene, formaldehyde, trichloroethylene, xylene, and ammonia from the air.

Kirsten Famiglietti, who has worked with the custom-container plantings at Van Wilgen’s, in North Branford, for the past five years, notes that while any plant will improve air quality in the home as it takes in carbon dioxide and releases oxygen, several plants are particularly good at removing chemicals and other toxins..

“Some cleaning products people use have chemicals that are left behind, and something like a snake plant will take that out of the air,” said Famiglietti. “The snake plant, by far, is the ultimate can’t-kill-it plant, as it’s low light and needs very little water.”

Other plants that Famiglietti recommends for improving air quality are peace lilies, Chinese evergreens, some palms, and any type of ferns.

“You don’t need 700 plants in your house,” she said. “Even one plant can make a difference. There’s something for everyone.”