The problem began in late July, when parents reported children coming home from Peri Park with flea bites.
"So around the end of July, we started getting reports from residents that the kids were coming home with bites after playing in the playground," Fairfax Public Works Director Kristin Arnold said.
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The town believes raccoons had been getting under a deck near the playground and brought fleas into the area.
Because Fairfax generally bans pesticide use on town property, crews first used a non-toxic steam treatment at the park.
"Since then we did see a dramatic drop under the playground area," Arnold said. "But the space shared a crawl space with the temporary fire station."
That shared space is how the town believes the fleas spread next door.
Fairfax's actual firehouse is being remodeled, so firefighters had been living and working out of a nearby town building serving as a temporary station.
Earlier this month, the town approved an exception allowing pesticides to be sprayed underneath that building. But this week, fleas were found inside as well.
That forced the crew and engine to relocate to Station 20 in Sleepy Hollow.
Town officials say emergency service continues, but some calls in Fairfax could take an extra minute or two while crews are based outside town.
Vice Mayor Frank Egger said the timing is especially concerning.
"We're in high fire season. This is not the time to be closing firehouses," Egger said.
At a special meeting Thursday, the Town Council unanimously approved another exception to the pesticide ordinance, this time allowing treatment inside the temporary fire station.
The vote came with concerns about firefighters later living and sleeping in a building that had been treated with pesticides.
Mayor Stephanie Hellman said the town had to balance its environmental rules with protecting first responders.
"It's not an easy decision, but a very clear one," Hellman said. "Sometimes, you have to make exceptions to protect the people that are serving our community."
Egger also raised concerns about chemical exposure.
"Firefighters run into enough problems with toxic issues, the fires they're fighting themselves," he said. "Put poison in their living quarters, doesn't make sense."
Councilmembers also said they want to revisit Fairfax's pesticide ordinance at future meetings after the flea response required multiple separate exemptions and treatments.
At Peri Park, half the playground has reopened. The town says it has not found fleas recently in the section that remains closed and hopes the rest can reopen soon.
The earliest firefighters could return to Fairfax is Monday.