Strange Smells in the House: Find the Cause by Smell

A strange smell in a house does one of two things. It is either a harmless nuisance, or it is the only warning you will get of a gas leak, an electrical fault or a chemical problem. This guide helps you tell which. It covers 45 smells people search for: 13 that call for action now, 15 to check soon, and 17 that are usually harmless.

Act Now If You Notice These

• Strong rotten egg or sulfur smell. Natural gas has no smell of its own. Gas companies add a rotten egg odor so leaks can be noticed. Poison Control says a strong sulfur smell makes a gas leak very likely. Connecticut's utility regulator says that if the odor is strong or you're unsure, leave the building right away and call your gas company from outside. Don't flip light switches, use a phone inside, or light anything. Don't go back in until the gas company says it's safe. You can also call 911.
• Burning plastic smell, or a warm outlet or switch plate. The U.S. Consumer Product Safety Commission (CPSC) lists a burning plastic smell and warm faceplates as signs of a wiring problem. Our judgment: stop using that outlet, switch off its breaker if you can do it without opening the panel cover, and have a licensed electrician look at it. If you see smoke or sparks, get out and call 911.
• Headache, dizziness and nausea in several people at once, with no smell. Think carbon monoxide. The CPSC calls it colorless and odorless. If a CO alarm sounds, don't look for the source. Move outside, call 911 or the fire department, and stay out until responders say it's safe.
• Someone swallowed a chemical, or has trouble breathing after fumes. Call Poison Control on 1-800-222-1222 (free, 24 hours). Call 911 for breathing trouble.

Find Your Smell

Dangerous smells are listed first. 12 of these smells have their own detailed page, linked from the table. The rest are explained further down this page, and the table links to each section.

Burning, gas and electrical smells

These smells can mean a gas leak, an overheating wire or a failing appliance, so they come first. Three rules cover all of them. A gas smell means leave the building and call your gas utility or 911 from outside, as Connecticut's utility regulator and Washington Gas both advise. Carbon monoxide has no smell, so only a working alarm warns you, and CPSC says to get outside and call 911 if you suspect poisoning. A burning or electrical smell means unplug what you can, switch off the circuit at the breaker if it is safe to reach, stop using that outlet or panel, and call an electrician. If you see smoke or flames, leave and call 911.

Burnt hair smell

I found no official source that separates a burnt hair smell from other burning smells, so treat it like any burning odor. The most likely cause is dust, hair or lint burning on a hot surface: a furnace or heater running for the first time in a season, a space heater, or a dryer. HVAC.com says dust burnoff is the most likely reason and should fade within a few hours.

If the smell lasts longer, or only shows up with one appliance, turn that appliance off and unplug it. Clean the lint filter and check the dryer vent, because UL says lint buildup is the main cause of dryer fires. An overheating motor or wiring can also smell like this.

Urgency: act if the smell comes from an outlet, switch or panel, or if it returns after cleaning. Cut the power at the breaker and call an electrician or an HVAC technician. Smoke means leave and call 911.

Burnt toast smell

If someone just used the toaster, old crumbs burning on the heating elements are the usual cause. Unplug it, let it cool, empty the crumb tray and shake out the rest. This is common manufacturer advice and my own judgment, not an official finding.

When nobody has been toasting anything, the smell is a warning. A burnt, acrid odor with no source can come from overheated wiring, and electricians link burning smells to overloaded circuits, melting wire insulation and failing outlets or breakers. A faulty appliance can cause the same odor.

Check first: is anything on, plugged in or cooking? Feel outlets and plugs near the smell. If one is warm, discolored or buzzing, stop using it and switch off that circuit at the breaker. Call an electrician if the smell has no explanation. Treat smoke as a fire and call 911.

Burning rubber smell

Hot rubber is one of the smells electricians list for overheated wiring, overloaded circuits and failing electrical equipment, so rule that out first. HVAC.com lists two other causes. Debris that fell into a vent can give off a burning plastic or rubber smell, and a clogged filter can make the blower motor overheat.

A slipping or worn belt in a dryer, vacuum or other motorized appliance can also smell like burning rubber. That is my judgment, not a sourced finding. Turn the appliance off and unplug it either way.

Urgency: act now. If the smell follows you from room to room, comes from a wall or outlet, or one appliance keeps producing it, shut off power to the affected area and call an electrician. For a furnace, turn it off and call a technician. If you see smoke, leave and call 911.

Metallic smell

A metallic smell has two common sources, and the first check is whether it comes from the water or the air. In water, EPA says copper, iron, zinc and manganese can all cause a metallic taste, and corroding iron or copper pipes can release them. Check each tap. TapWaterData says a hot-tap-only taste points to the water heater, and a cold-tap taste that is worst after the house sits idle points to your own pipes. Flushing the cold tap and seeing if it clears is a quick test.

A metallic taste does not tell you about lead. EPA says you cannot see, taste or smell lead, so only a lab test answers that.

In the air, HVAC.com says a metallic smell from a furnace is a reason to shut it off and call a technician. Urgency: soon for water, act for a metallic or hot smell from equipment.

Plastic smell

Two very different things smell like plastic, and you need to tell them apart quickly. A hot, acrid, burning plastic smell is an electrical warning. Electricians describe it as burning plastic or overheated electronics, caused by overloaded circuits, melting wire insulation or failing outlets. Do not use the outlet. Switch off the circuit, and call an electrician. A furnace or heater can do the same, for example when debris is trapped in a vent (HVAC.com).

A cold, chemical plastic smell from something new is usually off-gassing. EPA lists building materials, furnishings, office equipment and adhesives as sources of volatile organic compounds, and advises more ventilation. Open windows and see whether the smell fades over days.

Urgency: act if it is hot or comes from a wall, outlet or appliance. Low if it is from new products and fades.

Skunk smell

Treat a skunk smell as a possible gas leak until you know otherwise. The utilities I checked, including Washington Gas, Enbridge and Peoples Gas, describe the added odorant (mercaptan) as sulfur or rotten eggs, not skunk. Some people do describe the odor as skunk-like, but I could not confirm that with an official source, so it is my judgment to be cautious.

If you smell it indoors and no skunk is nearby, leave. Do not use switches, phones or the garage door opener inside. Call 911 and your gas utility from outside, and stay out until they clear the building. Utilities say not to look for the leak yourself.

If the gas company finds no leak, the likely causes are an animal that sprayed near or under the house, or sewer gas from a dry drain trap. Seal off the odor path and call wildlife control for an animal. Urgency: act until gas is ruled out.

Chemical, solvent and fuel smells

These smells share one thing: the gas you smell is the product itself evaporating. The EPA groups many of them as volatile organic compounds (VOCs), which can cause eye, nose and throat irritation, headaches, dizziness and nausea. Most are also flammable, so keep flames, sparks and cigarettes away from a strong smell. Open windows, move the source outdoors if you can, and keep it away from children and pets. If someone swallows a product or has trouble breathing, call Poison Control at 1-800-222-1222 (US, free, 24 hours) or 911. Nail polish, general chemical and mothball smells have their own pages.

Acetone smell

Acetone is a sweet, sharp solvent smell. It usually comes from nail polish remover, some paint thinners and strippers, or certain glues. NIOSH classes acetone as a highly flammable liquid with a flash point of 0°F, so vapor can ignite from a pilot light, a spark or a cigarette. Breathing it can irritate the eyes, nose and throat and cause headache and dizziness.

Check first for an open or leaking bottle, a spill under a sink, or a recently glued or painted item. Close the container, wipe the spill with a paper towel, and put the towel outdoors in a closed container (our judgment). Ventilate until the smell is gone. If the smell keeps coming back and you can't find a product, look at the other sections for a better match. Call Poison Control if someone swallowed it or feels unwell.

Source: NIOSH Pocket Guide, acetone.

Paint smell

Fresh paint smells because it releases VOCs as it dries. The EPA lists paints, lacquers, strippers and varnishes as VOC sources, and says they release gases while stored too. A paint smell in a room you just painted is expected. A paint smell with no recent painting usually points to an opened can, a varnished item, or old stored paint in a closet, garage or basement.

Ventilate well during and after painting, keep lids tightly closed, and follow the label. The EPA suggests discarding old partly used containers, because gases can leak even from closed ones, and not putting chemicals in the regular trash. Use a household hazardous waste collection instead. Our judgment: keep bedrooms and children's rooms ventilated for a few days after painting, and longer if anyone has asthma. Strong paint stripper or oil-based fumes in a closed room need fresh air at once.

Sources: EPA, VOCs and indoor air, EPA, Care for Your Air.

Turpentine smell

Turpentine has a sharp, pine-like solvent smell. MedlinePlus notes it is found in some paint brush cleaners and floor and furniture waxes as well as in pure turpentine. Likely causes are an open can, a recently cleaned brush, or a waxed or stained item. Fumes can cause dizziness, drowsiness and headache, so move to fresh air and open windows.

Seal the container and store it away from heat and children. Solvent-soaked rags are a fire hazard (our judgment, check the label): take them outdoors rather than leaving them in a bin inside. If someone swallowed turpentine, call Poison Control right away and do not make them vomit unless told to. For skin or eye contact, flush with water for at least 15 minutes.

Source: MedlinePlus, turpentine poisoning.

Kerosene smell

Kerosene smells oily and sharp. ATSDR says the most likely way to be exposed at home is a kerosene heater or stove, and lists vapors seeping into basements from contaminated soil as another route. Short-term breathing can cause nausea, headache, eye irritation and light-headedness. Swallowing even small amounts can be serious, especially for children.

Check the heater first: a smell while it runs or after refueling suggests a spill, overfilling or poor adjustment (our judgment). Turn it off, let it cool, wipe up the spill and ventilate. The EPA says unvented kerosene heaters produce carbon monoxide and nitrogen dioxide, so ventilate and keep a working carbon monoxide alarm. A strong fuel smell means no flames or sparks: leave and call the fire department. A smell in a basement with no heater may call for your local health or environmental department.

Sources: ATSDR, fuel oils ToxFAQs, EPA, Care for Your Air.

Diesel smell

A diesel smell indoors usually means fuel oil. ATSDR counts diesel and home heating oil among the fuel oils. Causes in order of likelihood (our judgment): spilled fuel in the garage or on clothes and boots, a stored fuel can, a fuel oil tank or burner leak if you heat with oil, or contaminated soil near the foundation.

If the smell is in the basement or furnace room, treat it as a heating system problem. Ventilate, light nothing, and call a licensed heating technician or your oil company. If the smell is strong, you feel dizzy, or oil is visible on the floor or near the tank, leave and call the fire department. Report a spill to your state environmental agency. ATSDR says short-term breathing of fuel oil vapors can cause headache, nausea and poor coordination, so don't stay in a strong smell.

Source: ATSDR, fuel oils ToxFAQs.

Asphalt smell

An asphalt smell is hot, tarry and bitter. Common causes are roofing work or hot sealing on your roof or a neighbor's, fresh paving or driveway sealer nearby, and asphalt-based roofing material or paint stored in a garage or attic. Wind can carry the smell in through windows and vents.

NIOSH says asphalt fumes are linked to eye, nose and throat irritation, and some studies report lower respiratory symptoms in exposed workers. Most home cases are short and come from outdoors. Close windows and vents on the side facing the work, and reopen them when the smell passes. If the smell is steady with no work nearby, check the attic and garage for stored material. See a doctor if you have breathing symptoms. Our judgment: ask the contractor how long the job will take.

Source: NIOSH, asphalt fumes update.

Tar smell

Tar smells smoky, like a hot road or an old wood fire. Likely sources are roofing or driveway work nearby, tar-based sealants, and tar-based products stored indoors. Roofing tar may be coal tar pitch or asphalt-based, so check the product label (our judgment).

The same steps apply as for asphalt: close windows facing the work, ventilate once the smell fades, and move any stored tar product outdoors in a sealed container. A smoky tar smell can also mean something is burning, so check for smoke, a hot wall or an overheating appliance. If you see smoke or suspect a fire, leave and call 911. Call Poison Control if someone swallowed a tar product.

Sources: NIOSH, asphalt fumes update, Poison Control, unknown fumes.

Rubber cement smell

Rubber cement smells like a strong, gasoline-like solvent. Many rubber cements and contact adhesives use hexane or similar solvents (check the label). NIOSH lists n-hexane as a highly flammable liquid with a flash point of minus 7°F and a gasoline-like odor. Its exposure effects include eye and nose irritation, nausea, headache and dizziness, and repeated exposure can affect nerves.

Check craft supplies, shoe repair glue, tire patch kits and recently glued flooring or trim. Close the container, ventilate, and work outdoors or by an open window next time. Keep it away from pilot lights and heaters. If the smell is strong enough to cause dizziness or headache, leave the room and get fresh air.

Sources: NIOSH Pocket Guide, n-hexane, Poison Control, unknown fumes.

Shoe polish smell

Shoe polish smells waxy and sharp. Poison Control lists waxes among household products that release VOCs. Usual causes are an open tin or bottle, a recently polished pair of shoes, or a closet or entry bench where polish is stored.

Close the lid tightly, wipe up any spill, and air shoes outdoors or in a ventilated space. Store polish away from heat, flames and children. Liquid polishes with solvents may be flammable (check the label). Call Poison Control if polish is swallowed. If the smell persists after you remove the polish, look at the other sections: damp, mold or leather can smell similar.

Sources: Poison Control, unknown fumes, EPA, Care for Your Air.

Vinegar smell

A vinegar smell is acetic acid. The plain cause is the most common: spilled or stored vinegar, or a cleaning solution made with it. Another likely cause is new silicone sealant. Soudal explains that acetoxy silicone releases acetic acid as it cures, giving a strong vinegar-like smell, while neutral silicone has a much lighter smell or almost none.

Check recent caulking around tubs, windows and sinks first, then the kitchen for spills or a leaking bottle. Ventilate: the smell from curing sealant should fade as it sets (our judgment). If there is no sealant work and no vinegar, look at drains, appliances and the other sections for a better match. Vinegar fumes can irritate the eyes and nose. Never mix vinegar with bleach.

Sources: Soudal, acetoxy and neutral silicone, Poison Control, unknown fumes.

Camphor smell

Camphor has a strong, medicinal, minty smell. NYC Health lists camphor in solid cubes or balls, balms and ointments, and vapor-steam products. It is toxic, especially to young children, and can enter the body by swallowing, breathing or skin contact. Symptoms such as seizures can start within 5 to 20 minutes.

Look for vapor rubs, balms, camphor blocks in closets or drawers, and moth repellents (mothballs are a different chemical, see their own page). Move camphor products out of reach, keep them in labeled containers, and ventilate. Don't scatter camphor around the home, use it for pest control, or add it to humidifier water. If a child swallows or chews a camphor product, or has a seizure, call Poison Control at 1-800-222-1222 or 911 at once. Avoid unlabeled camphor products.

Source: NYC Health, camphor.

Food, cooking and damp-house smells

Most smells that remind you of food come from food: spoiled leftovers, a full trash can, a drain with a dry trap or a film of residue, a fridge spill, or old cooking residue. Mold and damp can also read as sour, yeasty or "old tea." Start with the everyday causes, but rule out the exceptions first. A sweet or maple syrup smell near a car, boiler or heater can point to a coolant leak, and ethylene glycol, the main ingredient in antifreeze, is poisonous if swallowed (MedlinePlus). A coffee or burnt smell coming from an outlet or appliance is an electrical warning, not a kitchen smell (NFPA). A sour or musty smell that stays after cleaning can be mold behind a surface (EPA).

Maple syrup smell

A maple syrup smell has a few very different sources, so find where it is strongest. Check for something sweet and cooked first: syrup or sugar spilled on a hot burner, oven residue, or a spice or supplement that smells maple-like. Fenugreek seeds are used in maple syrup substitutes, and a fenugreek processing plant was the traced source of a long-running maple smell across New York City (Wikipedia). That points to outdoor air if the smell comes and goes with the wind.

If the smell is stronger in a garage or near a car, boiler or heating system, treat a coolant leak as possible. MedlinePlus describes ethylene glycol as sweet tasting and says to get medical help right away if it is swallowed. In the US, Poison Help is 1-800-222-1222. How strongly it smells is not well sourced, so judge by a puddle or a dropping coolant level, not the nose alone. Keep children and pets away from any puddle and call a mechanic or heating technician.

Sour smell

A sour smell usually means something is spoiled or growing. The most likely sources, in order: food gone off in the fridge or trash, a drain with built-up residue, damp laundry or cloths left wet, and mold. Check the fridge first, throw out anything doubtful, and wipe spills. The FDA says to keep the fridge at or below 40°F and to clean it often (FDA).

Then check where water sits. The EPA says to dry water-damaged areas within 24 to 48 hours to prevent mold, and that a moldy smell can mean hidden mold behind walls or under carpet. Small areas of about 10 square feet or less can usually be cleaned with detergent and water once the leak is fixed. Call a professional for larger areas, sewage water, or if the HVAC system may be contaminated. Never mix bleach with ammonia cleaners.

Rotten vegetables smell

This is almost always forgotten produce or a trash can. Look in the crisper, the pantry, under the sink, behind the fridge and in the trash and compost bin. A rotting potato or onion at the back of a cupboard can fill a whole room. Fruit flies appearing at the same time is a good sign you are close, since they breed in rotting produce, trash cans and drains (WSU).

Throw out the produce, wash the bin or crisper with detergent and water, and take the trash out. If the smell stays near the sink, check the drain and disposal. If it comes from a basement or crawlspace, look for damp and mold instead. If it smells more like sewage than vegetables, a dry drain trap is a common cause: pour a cup or two of water into rarely used drains, and call a plumber if that does not fix it (South Davis Sewer District).

Rotten fruit smell

A fermenting, rotten fruit smell means ripe or spoiled fruit, spilled juice or sugary residue. Fruit flies lay eggs near fermenting food, and common sites include overripe produce, drains, garbage disposals, empty bottles and cans, trash bins, and mops and cleaning rags (WSU). University of Georgia Extension also lists juice spilled behind the fridge, and says to replace trash bags that have been in use more than a few days (UGA Extension).

Find and remove the source first. Eat, discard or refrigerate ripe produce, clean spills, wash the trash can, and scrub drain walls with a pipe brush. To test a drain or disposal, tape a clear plastic bag over the opening overnight and see if flies collect in it. Traps help only after the breeding source is gone. If flies keep returning after all that, a pest control professional can help (judgement).

Curry smell

Curry smells that linger are usually cooking residue: spices and oils settle on fabric, the range hood filter and the walls, and leftover food smells strong in the fridge. Likely sources, in order: your own cooking, leftovers or a spill in the fridge, a trash can, and a neighbor's cooking carried through a shared wall or vent (judgement, not sourced).

Run the range hood while you cook, wash its filter, wipe nearby surfaces and soft furnishings, and take food waste out. If the smell has no food source and carries a hot or burnt note, treat it as an electrical issue: the NFPA lists a burning or rubbery smell from an appliance as a reason to call a qualified electrician (NFPA). Unplug that appliance and leave it off until it is checked. A plain curry smell is low urgency.

Yeasty smell

A yeasty or bready smell often comes from fermenting food: spilled beer or juice, dough or a sourdough starter, or old fruit. It can also come from a drain, where a film of food residue grows. The WSU fruit fly fact sheet lists fermenting food and moist organic material as the common breeding sites, which gives you a second clue (WSU).

Check the kitchen first, then bins, drains, bottles and cans. Clean drain walls with a pipe brush (UGA Extension). If the smell is musty rather than bready, or strongest in a damp room, treat it as possible mold: dry wet materials within 24 to 48 hours, fix the water source, and clean small areas yourself (EPA). Call a professional if the area is bigger than about 10 square feet or the smell has no visible source.

Pickles smell

A vinegar or pickle smell usually means fermenting or acidic food: an open jar, a leaking container, brine spilled in the fridge, or food scraps in the trash. It can also come from a drain with a film of residue, or from damp cloths and sponges left wet. Those are the common causes, in order. The FDA says to wipe up fridge spills right away and clean the fridge often (FDA).

Check the fridge door shelves and the back of the pantry first, then the trash and sink. Throw out leaking jars and wash the shelf with detergent and water. If you cannot find any food, check for damp or mold, because the EPA says a moldy smell can point to hidden mold. A pickle smell is low urgency unless it comes with a damp patch or water damage.

Citrus smell

A citrus smell is most often a product: a cleaner, dish soap, air freshener, candle or wipes with a citrus scent (judgement, not sourced). Rotting citrus fruit in a bowl, bag or cupboard also gives off a strong, sweetish smell, and it draws fruit flies. If a sweet note comes with a car, boiler or heating system, see the maple syrup section, since ethylene glycol is poisonous (MedlinePlus).

Check what was used recently, then check the fruit bowl, pantry and trash. If the smell is strong and comes with headaches or dizziness, ventilate the room and move out of it, because that points to an air quality problem. Citrus is low urgency when it matches a product or fruit. If it has no source and a person or pet feels unwell, call Poison Help at 1-800-222-1222 or a doctor.

Fried onions smell

A fried onion smell with no cooking is usually old cooking residue or food waste: grease on the range hood and walls, onion scraps in the trash or disposal, leftovers, or a neighbor's cooking through a shared vent. Check the trash, the fridge and the kitchen surfaces, then see whether it follows the wind or a particular vent (judgement, not sourced).

Take out food waste, wash the hood filter, wipe the walls and clean the disposal. If the smell is burnt rather than fried, or comes from an outlet, an appliance or a dryer, stop using it. The NFPA lists a burning or rubbery smell from an appliance, and discolored or warm wall outlets, as reasons to call a qualified electrician (NFPA). If you see smoke or flames, leave and call 911.

Tea leaves smell

A smell like damp tea leaves usually means damp organic material: wet tea bags or grounds in the trash or compost, a damp cloth, or a damp cupboard. It can also mean mold, which often smells musty or earthy. The EPA says a moldy smell can point to hidden mold, so check behind furniture, under sinks, around windows and in basements.

Remove food waste first. If the smell stays, look for water damage or condensation. Keep indoor humidity under 60 percent, ideally 30 to 50 percent, and dry wet items within 24 to 48 hours (EPA). Scrub small hard surfaces with detergent and water, and throw away wet porous materials such as carpet or ceiling tile. Call a professional for more than about 10 square feet of mold, sewage-contaminated water, or a contaminated HVAC system.

Fragrance and nature smells

Most smells in this group come from something scented that you or a neighbor brought in: candles, plug-ins, sprays, cleaners, essential oil diffusers, or a new wooden item. The EPA lists air fresheners, cleaners and building materials among the household sources of volatile organic compounds, and says to bring in fresh air when you use them. Cut grass can also drift in through open windows. If nothing explains the smell, a nose or sinus problem can cause "phantom" smells (see the perfume section). A sudden, strong smell with headache, nausea or dizziness is different: open the windows, leave if you're worried, and call Poison Control at 1-800-222-1222 (free, 24 hours). Carbon monoxide has no smell, so a pleasant scent never rules it out. If several people feel unwell at once, get outside and call 911.

Eucalyptus smell

A eucalyptus smell almost always means something scented is in the house: an essential oil diffuser, a spray, a candle, a vapor rub, a bath product or a bunch of dried stems. Check those first, then ask whether anyone has used a new cleaner or laundry product. Nothing about this smell points to a gas leak or a structural fault.

Switch off the diffuser or move the product, open a window, and the smell should fade within hours. Keep oils and diffusers away from pets. The ASPCA lists eucalyptus as toxic to dogs and cats, with drooling, vomiting, diarrhea, depression and weakness as signs. If a pet seems unwell, call a vet or ASPCA Poison Control at (888) 426-4435.

Oils can also harm children if swallowed. Poison Control advises keeping them locked away and calling 1-800-222-1222 after any swallowing. If there is no source anywhere, see the perfume section on phantom smells.

Pine smell

Pine usually comes from a pine-scented cleaner, an air freshener, a candle, a Christmas tree or wreath, or new pine furniture or flooring. Walk room to room and sniff the products and the newest wooden item in the house.

Fresh air does most of the clearing. For new furniture, the California Air Resources Board says smell alone doesn't prove formaldehyde, since varnishes and finishes also smell. It suggests opening windows, running exhaust fans, airing a new piece in the garage for a few days, and keeping heat and humidity down, because warmth and humidity raise emissions.

Pine oil products may bother pets. News reports citing the Pet Poison Helpline list pine oils among oils dangerous to cats and dogs, but I couldn't confirm that on the helpline's own site, so ask your vet about your specific product. Get help if the smell comes with headache, dizziness or throat irritation that eases when you leave the house.

Wax smell

A wax smell usually means a candle, wax melt, crayon, furniture polish or floor wax. Check for a candle that was burned recently or is still smoldering. A hot-wax or waxy-plastic smell with no candle around could also come from an overheating appliance part. That is my judgment, not a sourced finding, so don't ignore it if you can't find a source.

Scented candles and melts add fragrance compounds to the air like other scented products. One study of scented products found they released many VOCs, some hazardous, and that products labeled "green" or "natural" were no better. It tested air fresheners and similar goods, not candles specifically.

To clear the smell, snuff and remove the candle, open windows, and wipe any soot film. If you smell hot wax or burning and can't find a candle, switch off the likely appliance at the breaker and call an electrician. Leave the house and call 911 if you see smoke.

Perfume smell

If someone wore perfume, or a spray, plug-in or laundry product is nearby, the cause is easy. When nothing explains it, consider phantosmia, which means smelling something that isn't there. The Cleveland Clinic lists colds, sinus infections, allergies, nasal polyps, migraines, certain medications, dental problems and smoking as common causes. It says to see a provider if the smells last more than three weeks, and that rarely a neurological condition is behind it.

Sensitive people can react to real fragrance. A NIOSH workplace evaluation found that fragranced products can affect people with chemical sensitivities, allergies, asthma or migraines. If you get a headache or wheeze whenever a scent is on, remove it, ventilate, and talk with your doctor.

Vanilla smell

Vanilla is a common candle, wax melt, plug-in and room spray scent, and it's also in baking, lotions and car fresheners. Start there. If you didn't bake or burn anything, check laundry products, polish and anything a visitor brought.

A sweet, vanilla-like smell with no source may not be real. If it comes and goes with no product around, think about a phantom smell, and see a doctor if it lasts more than three weeks (Cleveland Clinic). A neighbor's cooking or dryer vent is another possible source, which is my judgment rather than a sourced finding.

To clear it, remove the scented items, open windows for cross-ventilation, and wash fabrics that hold the scent. Don't cover it with a stronger product. The study of scented products found fragrance ingredients usually aren't listed on labels, so removing the scent is cleaner than adding another.

Freshly cut grass smell

Indoors, a cut-grass smell most often means nearby mowing is drifting in through an open window, a door or the air intake, or that clippings came in on shoes or a pet. Some candles, sprays and cleaners also use a "fresh cut grass" fragrance. Check the doormat and your shoes first, then the scented products in the room. This ordering is my judgment, not a sourced finding.

If the smell is there with windows shut, no mowing outside and no scented products, look for stored clippings in the garage or a compost bin near a door. Damp clippings that sit and rot smell sour, not fresh.

To clear it, shut windows while neighbors mow, bring fresh air in afterward, and remove clippings. A grass smell can also be a phantom smell, so see a doctor if it lasts more than three weeks with no source (Cleveland Clinic). Call Poison Control if it comes with headache or dizziness.

When to Call Someone

• Gas utility or 911: any strong rotten egg or sulfur smell. Leave first and call from outside.
• Electrician: a burning plastic or burning hair smell near an outlet, a switch or an appliance, or a warm faceplate. Call 911 if you see smoke or sparks.
• Poison Control, 1-800-222-1222: anyone with symptoms after fumes, or anyone who swallowed a chemical.
• A plumber, heating technician or pest professional: when the smell points to a drain, a heating system or an infestation and you can't clear it with the steps in the table.

Frequently Asked Questions

What should I do if I smell natural gas?

Leave the building right away and call your gas company from outside. Don't flip light switches, use a phone inside, or light anything, and don't go back in until the gas company says it's safe. You can also call 911.

Does carbon monoxide have a smell?

No. The U.S. Consumer Product Safety Commission calls carbon monoxide colorless and odorless, so a working carbon monoxide alarm is the only warning. If one sounds, move outside, call 911 or the fire department, and stay out until responders say it's safe.

Is a burning plastic smell dangerous?

It can be. The U.S. Consumer Product Safety Commission lists a burning plastic smell and warm faceplates as signs of a wiring problem. Our judgment: stop using that outlet, switch off its breaker if you can do it without opening the panel cover, and have a licensed electrician look at it. If you see smoke or sparks, get out and call 911.

Why does a smell seem to fade after a while?

Your nose can stop noticing some smells after exposure. CDC and ATSDR guidance on hydrogen sulfide, the rotten egg gas, says the smell fades with exposure. A smell that seems to go away is not proof the problem has gone.

Who do I call if I can't place a smell?

Poison Control's guide to unknown fumes lists gas, mold, carbon monoxide and burning smells as the causes to rule out first. If anyone has symptoms or has swallowed something, call Poison Control on 1-800-222-1222, free and open 24 hours.

Sources

• U.S. EPA: Volatile Organic Compounds' Impact on Indoor Air Quality (VOC sources, effects, ventilation and storage)
• U.S. EPA: Care for Your Air, A Guide to Indoor Air Quality (ventilation and sensitive groups)
• U.S. EPA: Facts About Formaldehyde (composite wood, odor, irritation)
• U.S. EPA: A Brief Guide to Mold, Moisture and Your Home (hidden mold and moldy odors)
• Poison Control: Identifying unknown fumes in your home (causes, gas, mold, CO, burning smells, who to call)
• Poison Control: Chlorine gas (mixing bleach with ammonia or acids)
• Connecticut PURA: What to do if you smell natural gas (leaving and calling from outside)
• U.S. CPSC: Carbon Monoxide Fact Sheet (no smell, alarms, what to do)
• U.S. CPSC: Electrical Safety Month release (burning plastic smell and warm faceplates)
• CDC/ATSDR: Hydrogen Sulfide medical management guideline (smell fades with exposure)
• CPSC: Carbon Monoxide Information Center (Carbon monoxide is odorless; symptoms; get outside and call 911.)
• Washington Gas: Natural Gas Safety (Gas smells like sulfur or rotten eggs; leave immediately, avoid switches, call 911.)
• Enbridge Gas: Smell Gas (Odorant described as sulfur or rotten eggs; leave, do not hunt for the leak.)
• Peoples Gas: Safety, if you smell gas (Sulfur-like odor; leave, call 911 and the utility from a safe spot.)
• Mr. Electric: Burning Smells in Your Home (Burning plastic or rubber smells, overloaded circuits, melting insulation; stop using outlet, shut off power, call electrician.)
• HVAC.com: Heater Smells Like Burning (Dust burnoff, debris in vents, dirty filters, wiring smells, metallic smell; when to shut off and call.)
• UL: Mitigating Clothes Dryer Fires (Lint buildup in the vent is the main cause of dryer fires; clean the filter and inspect the vent.)
• EPA: Ozone Generators That Are Sold as Air Cleaners (Ozone health effects, ozone generators, outdoor sources and smell as an unreliable guide.)
• EPA: Secondary Drinking Water Standards (Copper, iron, zinc and manganese cause metallic taste; corrosion releases them.)
• EPA: Protect Your Family From Sources of Lead (Lead in water cannot be seen, tasted or smelled; flush and test.)
• TapWaterData: Metallic Taste in Tap Water (Hot versus cold tap pattern to locate the source of a metallic taste.)
• NIOSH Pocket Guide: Acetone (Acetone flash point, flammability and symptoms)
• NIOSH Pocket Guide: n-Hexane (Hexane flash point, flammability and symptoms)
• ATSDR: Fuel oils ToxFAQs (Kerosene and diesel home exposure and symptoms)
• MedlinePlus: Turpentine poisoning (Turpentine products, symptoms and first steps)
• NIOSH: Asphalt fumes update (Asphalt fume health effects)
• Soudal: Acetoxy and neutral silicones (Acetoxy sealant gives a vinegar smell as it cures)
• NYC Health: Camphor (Camphor products, risks and safe storage)
• Ethylene glycol poisoning (MedlinePlus) (Ethylene glycol in antifreeze is sweet tasting and poisonous if swallowed, get help right away, Poison Help 1-800-222-1222.)
• Electrical Safety Checklist (NFPA) (Burning or rubbery smell from an appliance, warm or discolored outlets and sparks are reasons to call a qualified electrician.)
• Fruit flies (WSU Pestsense) (Breeding sites in rotting produce, drains, trash and cans; drain test with a taped plastic bag.)
• Fruit flies (UGA Extension) (Trash bags, spilled juice, drains and pipe brush, find and remove breeding sources.)
• Are You Storing Food Safely? (FDA) (Fridge at or below 40F, food can be unsafe without smelling spoiled, clean fridge and wipe spills, discard doubtful food.)
• What's that smell? Sewer odors and P-traps (South Davis Sewer District) (Dry P-traps cause drain odors, refill with a cup or two of water, mineral oil slows evaporation, call a plumber if it persists.)
• Maple syrup mystery smell (Wikipedia) (A fenugreek processing plant was the traced source of a long-running maple smell in New York City.)
• CDC: About Carbon Monoxide (Carbon monoxide is odorless; symptoms; detectors)
• Poison Control: Essential oils (Keep oils locked away; call after swallowing)
• ASPCA: Eucalyptus (Eucalyptus is toxic to dogs and cats; symptoms; hotline)
• California Air Resources Board: Composite wood FAQ for consumers (Smell does not prove formaldehyde; ventilate, air in garage, keep heat and humidity down)
• Cleveland Clinic: Phantosmia (Phantom smell causes; see a provider after three weeks)
• NIH/PMC: Scented products emit a bouquet of VOCs (Scented products release many VOCs; green labels no better; ingredients not disclosed)
• NIOSH: Health hazard evaluation 2019-0240-3410 (Fragranced products can affect people with asthma, sensitivities or migraines)

The smell table and sections draw on these sources. Where a cause could not be confirmed, the section says so.