What burning gas adds to kitchen air
Gas range indoor air questions start with chemistry. Burning gas makes heat, water vapor and carbon dioxide, plus smaller amounts of other gases whenever combustion is less than perfect. EPA's indoor air pages put unvented gas cooking on their short list of indoor nitrogen dioxide sources, and name incomplete burning in gas ranges among the sources of carbon monoxide.
EPA notes that homes without combustion appliances average about half the outdoor level of nitrogen dioxide, while in homes with gas cooking, kerosene heaters or unvented gas space heaters, indoor levels often exceed the level outdoors. Nitrogen dioxide mainly irritates the eyes, nose, throat and airways; at low levels EPA links it to more reactive airways in some people with asthma and a higher risk of respiratory infections in young children.
Carbon monoxide, which has no smell
Carbon monoxide is not the gas you smell during a leak. It comes out of a flame that is short of air, and EPA describes it as colorless and odorless. EPA gives levels of 0.5 to 5 ppm in homes without gas cooking, 5 to 15 ppm near properly adjusted gas cooking appliances, and 30 ppm or more near poorly adjusted ones. The symptoms it lists include headaches, dizziness, nausea and flu-like illness that clears up after leaving home.
Where electric and induction ranges stand
A coil, radiant glass-top or induction range burns nothing, so it adds no combustion gases of its own. Cooking itself still sends smoke, grease and steam into the air on any range, which is why a hood earns its place over an induction range too, only for different reasons.
Source: EPA — Nitrogen Dioxide's Impact on Indoor Air Quality — Gas stoves are an indoor source of NO2; indoor levels in homes with gas stoves often exceed outdoor levels, about half outdoor levels without combustion appliances; health effects; install and use an exhaust fan vented outdoors over gas stoves; EPA — Carbon Monoxide's Impact on Indoor Air Quality — CO is colorless and odorless; incomplete combustion in gas ranges is a source; 0.5–5 ppm without gas stoves, 5–15 ppm near properly adjusted and 30 ppm or more near poorly adjusted stoves; symptoms; keep gas appliances adjusted and vent an exhaust fan outdoors
Getting real work out of the hood
EPA's first recommendation for both gases is the same: put a fan over the gas range that exhausts to the outside, and use it. Both halves of that advice matter. A hood that only recirculates air through a filter back into the kitchen catches grease but does not send combustion gases outside, and a ducted hood that is never switched on removes nothing at all.
A few habits make a working hood far more effective:
- Switch the fan on when the first burner lights, not once the kitchen already smells of dinner.
- Use the back burners when a pot fits there, since they sit most directly under the hood.
- Leave the fan running for a while after the last burner goes off.
- Keep the grease filters clean; GE's manual warns that grease should not be allowed to build up on the hood or its filter.
Air has to come back in from somewhere
A strong ducted fan pushes air out of the house, and the same amount has to find its way back in, which in a tight modern house can mean a window cracked open while cooking. Whirlpool's installation instructions add a warning about air moving the other way: never fit a ventilation system that blows down toward a gas range, because it can upset ignition and combustion.
Source: EPA — Nitrogen Dioxide's Impact on Indoor Air Quality — Gas stoves are an indoor source of NO2; indoor levels in homes with gas stoves often exceed outdoor levels, about half outdoor levels without combustion appliances; health effects; install and use an exhaust fan vented outdoors over gas stoves; EPA — Carbon Monoxide's Impact on Indoor Air Quality — CO is colorless and odorless; incomplete combustion in gas ranges is a source; 0.5–5 ppm without gas stoves, 5–15 ppm near properly adjusted and 30 ppm or more near poorly adjusted stoves; symptoms; keep gas appliances adjusted and vent an exhaust fan outdoors; GE Appliances — Owner's Manual, Electric Free-Standing Ranges (49-2000951) — Clean ventilating hoods frequently; grease should not accumulate on the hood or filter
What the flames say about combustion
The look of each flame is the everyday check anyone can make. GE's installation instructions describe normal flames as soft blue on natural gas, with some yellow tipping on the outer cones normal on propane, and call for service when the flames are yellow. Whirlpool's describe the bake and broil flames as a half-inch bluish-green inner cone inside a dark blue outer mantle, clean and soft, with no yellow tips and no blowing or lifting.
Flames that burn yellow, soot on the bottoms of pans or a flame that lifts off the burner ports mean the range is not burning cleanly, and a poorly adjusted flame is exactly where EPA's higher carbon monoxide figures come from. Setting it right is an adjustment for a technician; until then, keep that burner for short jobs with the hood running.
Flame colors that are not a problem
Not every odd color means poor combustion. Whirlpool explains that an ultrasonic humidifier anywhere in the house can carry minerals into the flame, calcium turning it orange or red and potassium lilac or pink, and GE notes that particles in a newly connected gas line can give an orange flame that soon clears. Judge the whole flame, not a flicker of color at its tip.
Source: EPA — Carbon Monoxide's Impact on Indoor Air Quality — CO is colorless and odorless; incomplete combustion in gas ranges is a source; 0.5–5 ppm without gas stoves, 5–15 ppm near properly adjusted and 30 ppm or more near poorly adjusted stoves; symptoms; keep gas appliances adjusted and vent an exhaust fan outdoors; GE Appliances — Installation Instructions, Gas Range (31-2001181) — Soft blue flames normal on natural gas, yellow tips on outer cones normal on propane, yellow flames call for service; Whirlpool — Installation Instructions, 30-inch Freestanding Gas Ranges (W10658550B), archived whirlpool.com copy — Bake and broil flames: 1/2-inch bluish-green inner cone, dark blue outer mantle, no yellow tips, blowing or lifting; do not install ventilation that blows air downward toward the range
Habits that make the air worse
GE's owner's manual for its single-oven gas ranges lists several uses that raise carbon monoxide or starve the burners of air. Each looks harmless, which is why they are worth knowing:
- Using the range as a space heater to warm the room, which GE says can cause carbon monoxide poisoning and overheat the oven.
- Setting an after-market grill plate over a gas burner, which GE says causes incomplete combustion.
- Putting a wok support ring over a burner or grate instead of standing a flat-bottomed wok on the grate.
- Covering the oven bottom, its slots or a whole rack with foil or liners, which blocks the air the oven burner needs.
- Blocking the range's air openings at the back of the top, around the oven door or under the drawer.
Source: GE Appliances — Owner's Manual, Single Oven Gas Ranges (49-2000316) — Never use the range as a space heater (carbon monoxide, oven overheating); after-market grills cause incomplete combustion; no wok support rings; no foil on the oven bottom or whole racks; never block the range's air openings
Alarms, checkups and when to call
Because carbon monoxide gives no warning of its own, an alarm is the practical way to know it is building up. Nicor Gas reminds customers that carbon monoxide comes from incomplete burning of any common fuel, including natural gas and propane, and that alarms need testing often and replacing when they reach 10 years old. Some states set rules on where they must go; Illinois, where Nicor operates, requires one within 15 feet of every sleeping room.
Book a look at the range when flames stay yellow after the burner caps and ports have been cleaned, when pans keep coming away sooty, when the kitchen feels stuffy and headache-inducing during cooking, or after the alarm has gone off. If the carbon monoxide alarm sounds, get everyone out into fresh air and call 911 or the fire department from outside first; the range comes after.
Source: Nicor Gas — Emergency information: Carbon monoxide — CO comes from incomplete combustion of common fuels including natural gas and propane; test detectors frequently and replace every 10 years; Illinois requires an alarm within 15 feet of every sleeping room
