Nearly 450 homes near O’Hare and Midway airports have a foul odor coming from their city-installed sound-reduction windows, according to the latest tally of complaints investigated by city officials.

Approximately 55 percent of all homes investigated by crews working for the city tested positive for the smelly sound-insulation windows, according to the Chicago Department of Aviation.

In all, the city has received 949 calls about smelly windows and tested the air quality in 88 percent of the homes, Aviation Department officials said.

An initial round of testing by Amec Foster Wheeler Environmental Infrastructure  found “no evidence” that the windows had “any significant impact on indoor air quality or related health concerns.” A second round of testing is now underway to “understand the root cause of the odorous windows issue,” Aviation Department spokeswoman Lauren Huffman said.

Testing in homes will continue as the weather warms up, which exacerbates the smell by heating up the windows and the insulation around them.

“We remain committed to fully understanding the cause of this issue and the right solution to address it, Huffman said. “The second phase of odorous window testing is underway today, and we look forward to bringing more insight into this issue to the community this spring.”

The pace of complaints lodged with city officials slowed considerably this winter, with 39 calls from homeowners near Midway and 14 from homeowners near O’Hare during January, February and March, officials said.

Ald. Marty Quinn (13th) said he planned to launch an outreach campaign to residents of his Southwest Side ward near Midway to schedule testing once the weather warms up for good.

“A lot of questions still remain,” Quinn said, adding that he wants to see all of the different brands of windows tested to see if they emit noxious gases as well as the material used to install the windows. “From my vantage point, a lot of work still needs to be done on this issue.”

Only nine homes were tested during the first round, which means any results are “inconclusive,” Quinn said.

“You can’t draw any conclusions from nine homes,” Quinn said.

By the end of the month, the Aviation Department will send a letter to the owners of all “eligible” homes where sound installation has been installed to invite them to have the air quality in their homes tested, officials said.

“I want all the homes tested,” Quinn said. “We are going to drill down on this issue.”