6 Weird House Smells: Which Ones Are Concerning?

By Courtney Klosterman, home insights expert at Hippo home insurance.

Unpleasant odors in a home can be more than just a nuisance. Sometimes, weird smells in the house can be early warning signs of underlying problems that may lead to bigger issues down the road. 

Taking the time to identify and address the source of these smells can prevent them from becoming a nuisance and, more importantly, stop small problems from turning into costly repairs. Here are some home smells that may require immediate attention.

1. Fishy Odor

Level of urgency: High

A fishy odor wafting through your house may seem harmlessly unpleasant, but you shouldn't ignore it. This smell can have a surprising culprit: electrical issues. 

When electrical components like wires or outlets overheat, the burning plastic insulation can emit a distinct fishy odor. It indicates potential overheating that could lead to electrical fires.

Common locations:

• Walls near light switches or outlets
• Around electrical panels, typically located in garages or basements 
• Near appliances that have recently been overworked or are breaking down 

Actions to take:

• Turn off and unplug any appliances that were recently in use.
• Do not use any outlets or switches that feel warm to the touch.
• Call a qualified electrician to diagnose the problem and make repairs. Don't attempt to fix electrical issues yourself.

Preventative measures:

• Plug in fewer appliances at once to help avoid overloading or overheating circuits.
• Have electrical systems inspected annually, especially if the home is older.
• Replace any worn outlets or switches, as using outdated or damaged outlets and switches can increase the risk of electrical fires and other hazards.
• Unplug appliances when not in use to prevent overheating, such as toasters, space heaters and irons.

2. Sewage

Level of urgency: Moderate to high

Sewage smells are unmistakable and unpleasant. In addition to putting a damper on summer entertaining, they could signal a potential problem with the plumbing system. 

The urgency of sewage smells can range from moderate to high, depending on the problem. They could indicate backed-up plumbing, but stronger odors could mean a larger problem that shouldn’t be ignored. 

Methane, one of the main gases in sewage, can become flammable or leak into the home, posing a serious health risk. A buildup of the gas can occur due to several plumbing issues, including:

• Leaking or cracked pipes: Damaged pipes can allow sewer gas to escape into a living space.
• Blocked air vents: Vent pipes are crucial for venting sewer gases safely out of a home. Blockages in these vents can trap the gas indoors.
• Clogged drains: Severe clogs can prevent proper ventilation and lead to a build-up of sewer gas.
• Dry P-traps: The U-shaped pipe under sinks and drains, known as the P-trap, holds water to create a barrier between sewer gases and the home. If this water evaporates due to infrequent use, sewer gas can seep back up.

Common locations:

• Bathrooms, especially around the toilet or shower drain
• Kitchen drains
• Floor drains in basements or laundry rooms
• Around vent pipes on the roof or exterior of the house

Actions to take:

• Identify the source of the smell by checking drains for clogs, inspecting for leaks around pipes or toilets, and ensuring vent pipes are clear.
• If you're comfortable with DIY plumbing maintenance, cleaning a sink’s drain trap could address the issue. Unscrew the slip nuts holding the trap in place, empty the trap, clean any debris and reassemble the trap with fresh washers to help ensure a tight seal.
• Run plenty of water down affected drains to flush out any debris.
• For persistent smells or leaks, call a licensed plumber to diagnose and repair the issue.

Preventative measures:

• Avoid pouring grease or food scraps down drains.
• Regularly pour boiling water down drains to prevent grease buildup.
• Have your sewer line inspected and cleaned professionally every few years.

3. Ammonia

Level of urgency: High

While some cleaning products contain ammonia, a lingering ammonia smell that isn't cleaning-related could indicate a couple of issues. A strong ammonia smell near your refrigerator could be a sign of a leak in the coolant lines or defrost pan. This is a high-urgency issue, as a refrigerant leak can damage the appliance and potentially cause a fire hazard. 

Washing machine hoses also can deteriorate over time, causing a leak that releases ammonia from the cleaning products used. A strong ammonia smell in crawl spaces or behind walls also could indicate a decomposing rodent or small animal, which you should take care of promptly to avoid attracting pests and creating unsanitary conditions. 

Common locations:

• Kitchens near refrigerators or freezers
• Utility rooms or laundry rooms near washing machines
• Around floor drains
• Bathrooms near drains or toilets (less common)
• Behind sheetrock
• Inside crawl spaces where small animals could get in

Actions to take:

• Check for leaks around refrigerator coolant lines or defrost pans. Consider a smart-home upgrade, like a water leak detector, to get alerts to leak issues.
• You also can manually inspect washing machine hoses and connections for leaks. Look for signs of animal decomposition near floor drains or crawl spaces.
• Turn off and unplug any appliances suspected of leaking.
• Open windows and doors to ventilate the area.
• For strong ammonia smells or suspected leaks, call a qualified professional.

Preventative measures:

• Inspect washing machine hoses for cracks or wear and tear and replace them when necessary.
• Maintain proper ventilation in crawl spaces and around floor drains.
• Seal any gaps or holes around pipes that could allow rodents to enter your home.
• Replace washing machine hoses every five to seven years.

4. Rotten eggs

Level of urgency: High

A rotten egg smell is one of the most concerning odors in a home. This unpleasant scent is known to be an indicator of a gas leak, commonly caused by natural gas, propane or hydrogen sulfide. Ignoring this smell can pose serious risks, including fire hazards and health issues due to gas inhalation. 

Common locations:

• Around gas appliances like stoves, water heaters or furnaces
• Near gas pipelines or connections
• In poorly ventilated areas or crawl spaces

Actions to take:

• Evacuate the house immediately and leave the doors and windows open while you wait for the gas company to arrive.
• Immediately call your gas company or a qualified technician to inspect and repair the gas leak.
• Do not turn any electrical devices, switches or appliances on or off, as they can ignite the gas.
• Turn off the main gas valve to your house if you can locate it safely. The valve is usually near the meter outside your house.

Preventative measures:

• Regularly have your gas appliances serviced by a qualified technician.
• Install carbon monoxide detectors in your home and test them monthly.
• Avoid using a gas oven or stove for space heating.

5. Damp or musty

Level of urgency: Low to moderate

A persistent damp or musty odor in a house can be more than unpleasant but a sign of a moisture control problem. This smell is often associated with mildew growth, a relative of mold that thrives in damp environments. Leaky pipes, roofs or air conditioners can all create excess humidity and lead to overly damp environments. 

While a musty smell in the house isn’t immediately harmful, ignoring the smell can lead to the spread of mildew and mold spores, which can cause allergies or respiratory issues. Luckily, getting rid of mold or mildew isn’t hard to do if you spot it early.

Common locations:

• Basements
• Attics
• Bathrooms (around showers or tubs)
• Kitchens (around sinks or under appliances)
• Closets
• Areas with poor ventilation

Actions to take:

• Locate the source of moisture or water intrusion that is causing the dampness and musty smell. Look for leaks around pipes, windows or the roof. Check for condensation on walls or pipes.
• Increase airflow by opening windows, using exhaust fans or installing a dehumidifier to reduce humidity.
• Repair leaky pipes, roofs or faucets.
• For small areas of mold or mildew, mix a solution of water and white vinegar and scrub the affected area. For extensive and clearly visible mildew growth, consult a professional remediation company.
• Regularly inspect and maintain the home's plumbing, HVAC system and roof to prevent water damage and moisture buildup.
• Consider mold insurance, but review your home insurance policy to understand which types of mold issues are covered.

Preventative measures:

• Use exhaust fans in bathrooms and kitchens when in use. Open windows to allow fresh air circulation, especially after showering or cooking.
• Dry damp surfaces promptly. Don't let wet towels or clothes pile up. Wipe down condensation on walls or windows.
• Regularly check around pipes, faucets, windows and the roof for signs of moisture buildup.

6. Sweet

Level of urgency: Low to moderate

A sweet smell in your home might seem pleasant, but it can indicate a serious issue, like a coolant leak from a refrigerator, air conditioner or heat pump.

Air conditioners and refrigerators rely on coolant to function. But coolant can be toxic if inhaled or ingested, so promptly addressing a leak is important. Besides possibly harming your health, it also could damage your appliances if not fixed. 

The urgency depends on the location and strength of the smell. A faint sweetness near a refrigerator might be a low-urgency concern while a strong, syrupy odor near your air conditioner could be a high-urgency issue.

Common locations:

• Around air conditioning units or refrigerators
• Near heat pumps
• Under sinks or near cabinets (if there's a leak behind them)

Actions to take:

• If you suspect a coolant leak, turn off your air conditioner or refrigerator at the breaker box outside your home. Also, check for visible leaks around the appliances or under the cabinets.
• Do not touch or inhale the coolant chemicals, and avoid consuming any food or drinks that may have been exposed.
• Don’t attempt to fix suspected coolant leaks yourself. Call a qualified HVAC technician to diagnose the leak and make repairs.

Preventative measures:

• Schedule regular maintenance for your air conditioner and refrigerator.
• Inspect for leaks around these appliances periodically.

Tips to Minimize Odors

While unpleasant smells might be unavoidable sometimes, you can take proactive steps to minimize some and keep your home smelling fresh. Here are a few odor-busting tips to help:

1. Perform regular cleaning: Regularly clean and disinfect surfaces to remove odor-causing bacteria and grime. Pay special attention to areas like kitchens, bathrooms and garbage cans.
2. Use odor eliminators: Use sprays on fabrics and gels or packs for ongoing odor control in problem areas. You can also keep bowls of baking soda or white vinegar in high odor areas to absorb and neutralize mild smells.
3. Use natural ventilation: Open windows and doors whenever possible to allow fresh air circulation and remove stale odors.
4. Get an air purifier: Invest in HEPA air purifiers for rooms prone to lingering odors. These can help trap dust, allergens and odor particles.
5. If other strategies don’t work, or you suspect a serious issue, like a gas leak, call a professional. A qualified plumber, HVAC technician or remediation company can diagnose the source of the odor and take the necessary steps to eliminate it safely and effectively.