Weird house smells: What they mean and when to get help

The gurgling of a household sink working in concert with the stench of sewage, home inspector Rob Byrne ran the water. Something was wrong.

He checked the main house trap. Byrne smelled the fumes — sulfuric, eggs-past-their-prime-like — emanating from a backed-up sewer.

"You could see the water coming out," said Byrne, of Higher Elevation Home & Commercial Inspections LLC; but the smell was a key indicator of what was happening.

A home is a nuanced aromatic environment. The smell of sauteed onions on the kitchen stovetop mingles with candle scents and hints of neon-colored household cleaners. Occasionally, though, a smell stands out as a signal that a deeper issue needs addressing.

Home insights expert Courtney Klosterman, of Hippo Home Insurance, recommends taking notice of the smells of sewage, fish, ammonia, rotten eggs, dampness or mustiness and coolant. In the summer months, she cautions, it is particularly important to pay attention to the musty smell that can indicate the presence of mold. 

"As our homes age, they’re ultimately going to start to begin to break down," Klosterman said. "The best approach is really a proactive one, so that you're not having to deal reactively in the moment, which can increase costs."

Klosterman recommends completing seasonal home walk-arounds and maintenance. The cost of maintenance and repairs will vary from home to home, depending on the home's age, construction and area climate, she said. 

"It’s really important to understand what your household budget is for unexpected repairs," she said. "Financial experts recommend having around 1 to 3% of your home’s value in savings for unexpected repairs and other home costs that could come up."

'Musty basement smell'

For the past three decades, Dominick Manieri has used his nose for work. Through his company, Long Island Mold Guy, Manieri offers mold inspection, odor removal and water damage restoration services. 

"If it's just a random odor, I'm going to use my nose because I feel I have a very keen sense of smell," Manieri said. "I'm going to look through and try to actually find the source of that odor, just based on what I'm smelling and what the customer is telling me."

Manieri described the smell of mold as "a musty basement smell." This odor is of great concern to homeowners, he said.

"It could be a water issue from the foundation, a leak, or they may, in fact, already have a mold problem," said Manieri, who is based in Centereach and services all of Long Island. 

Mold, dead animals

In the attic, Byrne said there are two common smells: dead animal, or mold.

"Clearly, there’s a big distinction between mold in the attic and a dead animal," he said. "I mean, it’s like vanilla and chocolate ice cream."

These distinct smells each come with its own visual evidence of the mold or animals.

"Here’s another thing — animals nesting in the attic," he said, of creatures who make a home out of insulation. "Either way, what happens is, once the insulation gets contaminated, you have to get rid of it."

Recently, Manieri traced an unidentified smell to a dead squirrel in a homeowner's crawl space.

"It has to be taken away, and the area surrounding it be cleaned and disinfected and deodorized," he said. "And that entry has to be sealed off, too."

Sewage

The smell of sewage can indicate a waste line leak, Manieri said. Sometimes, this means a slow leak from a cast-iron waste line, he added. 

"The customer won't even know about the cracked line until that odor starts permeating the air," Manieri said. "It smells almost similar to a bathroom odor."

Oil

"A lot of times we smell oil," Byrne said. "If there’s an indoor oil tank, sometimes we go down in the basement, we smell the fumes from the oil, or the oil tank."

Sometimes, he said, an oil tank is placed behind a wall.

"We can’t see behind it, but you can smell it, and you know that there’s a concern," Byrne said.

Natural gas

Inherently, natural gas does not have a smell.

"What the gas company does is, they actually put a scent in the gas, so if you have a gas leak you smell that [additive]," Byrne said.

The odor widely recognized as "gas," used for heating homes, is the additive mercaptan, or methanethiol. The strong smell makes colorless, odorless natural gas more easily detectable.

"A gas leak is way concerning because the house could blow up," said Byrne. "But, dead animals, or animals nesting in the insulation is an environmental concern, because now you’re dealing with urine, feces, and it could be a health hazard"

Coolant

While coolant, used in air conditioning, refrigeration and heat pump systems, does have a sweet smell, Byrne said it usually leaks too slowly for the scent to serve as an alarm.

By Arielle Dollinger

arielle.dollinger@newsday.com@aridollinger

Arielle Dollinger joined Newsday as a staff reporter in 2022. Previously, she covered local and national news as a freelancer for The New York Times, Newsday and other outlets.