Gas: the smell and the valve

When you smell gas at home, the obvious thing to do is the dangerous one. You reach for the light switch to see better, or, in the US, where one utility says doorbells and phones can spark, you ring the neighbour's bell or pick up your phone in the kitchen. The gas companies' advice on what to do instead is short, specific and, between the UK and the US, different at the very first step. Here are each country's steps in full, as the gas companies give them, and what to do when you can't smell anything. Then two leaks, one in a British flat and one in an American house. You'll finish with a card you could follow in the dark.

The box gives the short version of the gas steps, and it splits them by country because the UK's gas networks and American utilities tell you different things. This lesson gives each in full. Follow your own country's, never the other one's.

Lesson 1, "How a house works, and where it switches off", found the emergency control valve beside the meter and asked you to look at it without turning it. This lesson is about the night you might need it, and the nights you should leave it alone. Who may work on gas, and how to check the engineer who comes, is lesson 10, "Gas: the law and the engineer".

If you smell gas: the UK steps

In Great Britain

Great Britain has several gas networks, the companies whose pipes bring gas to homes, and one emergency number for all of them. This course read two sets of steps, not every network's.

National Gas, which runs the national transmission system, says "these emergency guidelines apply to all gas users", and gives them in five lines:²

• "Do not smoke or light matches."
• "Do not turn electrical switches on or off."
• "Open doors and windows."
• "Turn off the meter at the control handle unless the meter is in the cellar."
• "Call the National Gas Emergency number (0800 111 999)."

The number belongs to the National Gas Emergency Service, it is free, and it is answered day and night.¹ Because National Gas's guidelines cover all gas users, it does not depend on which company sends your bill.

Cadent runs the largest network, covering the North West, the West and East Midlands, the East of England and North London, and gives fuller steps for its own customers.¹ Before you call:

• "Open doors and windows to ventilate the property."
• "Turn off the gas at the mains tap. This can usually be located near the gas meter and has a handle that can be turned 90 degrees. If the gas leak is in a cellar or basement, do not enter and instead evacuate the building."

And what not to do: turn any power or light switches on or off, light any sort of flame within the property, or "Use any appliances that could cause a spark." Then: "Once you're safe, call the National Gas Emergency Service number on 0800 111 999". Afterwards: "Always wait until the gas engineer has given you the all-clear before returning inside your property." The engineer will need to get in to make it safe.¹

Great Britain's Health and Safety Executive (HSE) gives a shorter list on its page for home owners: call the emergency number, open all the doors and windows, and "Shut off the gas supply at the meter control valve (if you know where it is)". HSE's list has no cellar condition and says nothing about switches.⁴ Its page still calls the number National Grid's, an older name; the number is the same.

Cadent's "mains tap", National Gas's "control handle" and HSE's "meter control valve" are one handle, the one lesson 1 called the emergency control valve. Once it's off, it stays off: Cadent says "Don't turn it back on until advised it's safe to do so."¹

Read the two cellar conditions closely, because they are not the same. Cadent's is about where the leak is: if it is in a cellar or basement, do not go in, and get out of the building. National Gas's is about where the meter is, "unless the meter is in the cellar", and it says nothing about leaving. They come apart when the meter is in a cellar and the smell is upstairs. This course's reading is to take both: if either the smell or the meter is in a cellar or basement, nobody goes down to the valve. One more condition is this course's own, from the box at the top: "if you can do it safely", which here means reaching the handle without going further into the smell.

Then, do you stay in or get out? Neither British page says in so many words to leave the building, except for a leak in a cellar or basement. But Cadent says to call "once you're safe" and to wait for the all-clear "before returning inside your property", which assumes you are outside. So this course's reading, for anywhere in Great Britain, is: switches alone, doors and windows open, the meter off if neither condition stops you, then everyone out, the call made from outside, and nobody back in until the engineer says so. Cadent writes for its own network, and this course did not read the other networks' pages; nothing on National Gas's or HSE's page says otherwise.

Two more cases. If the smell is outside, Cadent says to call the same number as soon as you can, not to light any naked flame nearby, and to wait for the emergency engineer.¹ And if you or your builder hit a gas pipe while digging or drilling, National Gas says to call 0800 111 999 "day or night", even if no gas seems to be escaping.²

In Northern Ireland

Northern Ireland has its own number, 0800 002 001, for the Northern Ireland Gas Emergency Service. This course read two pages that give the same steps: Phoenix Energy, a gas network company there, and SSE Airtricity, one of the suppliers.³⁸ Both put the call first. SSE opens: "If you smell gas or you are worried about gas safety, phone the 24-hour Northern Ireland Gas Emergency Service on 0800 002 001." Phoenix's first step is "Call the gas emergency team 0800 002 001". Then, in SSE's order:³

• "Turn off the gas supply at the meter, unless the meter is located in a cellar or basement", in which case, it says, do not go in.
• If the smell is in the cellar or basement, get out of the building.
• "Extinguish all naked flames and do not smoke or strike any matches."
• "Open doors and windows for ventilation."
• "Check gas appliances to see if the gas has been left on unlit or that a pilot is out." (A pilot light is a small flame some appliances keep burning.)
• Do not turn any electrical switches on or off, "including door entry systems".

Both pages end the same way: "Never leave it to anyone else to call", and make sure you "allow immediate access" to the engineer.³⁸ Neither says to leave the building unless the smell is in a cellar or basement.

If you smell gas: the US steps

American utilities start somewhere else. Con Edison, in New York: "Leave immediately and take others with you." If the leak is outside, move to a safe spot far away. Then call 911 or the utility. Three more of its lines are worth learning word for word:⁵

• "Even if the odor isn’t very strong, you should still leave the area immediately, taking others, and then call."
• "Don’t assume someone else has already called."
• "Don’t light a match, smoke, flip a switch, ring a doorbell, or touch appliances or electronics, including your phone. Doing so can produce sparks that might cause the gas to explode."

SoCalGas says "IMMEDIATELY EVACUATE THE AREA and call us from a safe location", and to call 911 from a safe place too if life or property is at risk. Its list of things not to do differs from Con Edison's. It has no flame of any kind and "DO NOT turn electrical appliances or lights on or off", and it adds motorized equipment, vehicles and any device that could cause a spark, and "DO NOT attempt to control the leak or repair a damaged pipe or meter." It does not mention doorbells or phones.⁶

Atmos Energy: "leave the area immediately! From a safe distance call 911" and the utility's own emergency line, and "Do not assume someone else will report the leak."⁷ Atmos's page says nothing about switches or flames.

None of the three leak pages tells you to open windows or to turn anything at the meter, and SoCalGas's tells you not to try to control the leak at all. So on those three pages, when you smell gas at home you leave and call, and you do not go to the meter. But US utilities do not all say the same thing everywhere. SoCalGas's separate earthquake and emergency page tells its customers to turn off the meter if they smell gas, "and ONLY if it is safe to do so", and to leave it off once it's off.⁹ Your own utility's page decides, and this course read three. Find it now, follow it, and copy its emergency number from its website or your bill before you need it.

The two side by side

Put side by side, and this is this course's summary: every page read sends you to an emergency line, and every page that gives a list of things not to do (Cadent, National Gas, SSE Airtricity, Phoenix, Con Edison, SoCalGas) rules out a flame and touching a switch. Atmos's page and HSE's short list mention neither. What they do not share is the first move: in the UK you ventilate and turn the gas off at the meter; in the US you leave first and touch nothing. None of the sources read says why the advice differs between the countries, and this course won't guess. Learn your own country's, and don't borrow the other's.

When you can't smell it

Natural gas has no smell of its own. Con Edison explains that a chemical called mercaptan is added so that you can detect a leak, and that many people compare its smell to rotten eggs.⁵ The smell is the alarm, and the alarm can fail.

It can fail in you. SoCalGas says you may not smell leaking gas if your sense of smell is diminished, if you've been around it long enough to stop noticing (odour fatigue), if a cold, sinus trouble or allergies have blocked it, or if other smells mask it.⁶ Cadent points people who have lost their sense of smell to SmellTaste, a charity for people with smell and taste disorders.¹

And it can fail in the gas. SoCalGas says the odorant can be lost, "making it undetectable by smell", and that this "odor fade" is more likely in four situations: in new steel pipe that was recently made or hasn't carried odorised gas before; in systems at higher pressure, and when the flow is limited or intermittent; where rust, moisture or other substances are in the pipe; and depending on how the customer's own piping is designed and built, such as its length and diameter. Its conclusion: "it's important to not rely only on your sense of smell to be alerted to a natural gas leak."⁶ Con Edison's list is similar. It includes plastic as well as metal pipe, and says that when a leak is underground, the soil around it can cause odour fade.⁵ Atmos says how often it happens: for most people smell is "a highly reliable indicator of a natural gas release", and it calls the gas's own smell fading something that happens in "certain rare situations".⁷ This is the US utilities' account of their own pipes. The UK pages this course read do not discuss odour fade.

So the other senses matter. SoCalGas lists hissing or whistling, dirt or water blowing into the air, and a dry patch of grass. Con Edison adds a white cloud, bubbles in water, blowing dust, dying plants, and a roar.⁵⁶ If you suspect a leak but can't smell it, Con Edison says you should "still find a phone away from the area and call".⁵

Two US utilities go a step further for their own customers. Con Edison says "A slow gas leak may not produce enough scent to be detectable" and that "A gas leak detector can give you peace of mind", and Atmos says "residential methane detectors are commercially available and can provide an additional ability to detect the presence of gas".⁵⁷ That is Con Edison's and Atmos's advice, for US homes, and this course names no product. This course read no British page on gas detectors, for them or against them.

One more thing a smell can't tell you about: a carbon monoxide alarm is not a gas alarm. Con Edison says most carbon monoxide detectors "do not detect combustible gasses", and to check the label.⁵ Carbon monoxide, which has no smell at all, is lesson 11, "Carbon monoxide and the alarms that warn you".

Two leaks, worked through

A shared flat at eleven at night

The simple case first, in Great Britain. Isla lives in a shared flat in a converted Victorian house in the Black Country, in the West Midlands, on Cadent's network. At eleven at night she comes back to a strong smell of gas in the hall. The meter is in a cupboard by the front door. Two flatmates are in their rooms.

She works through Great Britain's steps.

1. The switch. The hall light is off. She leaves it off and doesn't touch the switch by the door (Cadent, National Gas).¹²
2. Air. She opens the front door and the hall window (Cadent, National Gas).¹²
3. The meter. The meter is in a cupboard and the smell is in the hall, so neither is in a cellar or basement and neither network's condition stops her. She can reach the handle without going further into the smell, which is this course's condition, so she turns it a quarter turn, the way Cadent's meter page describes.¹²
4. The flatmates. She knocks on their doors and tells them to come out with her, so that all three are out of the flat before she calls. Nobody uses a switch or an appliance on the way.¹
5. The call. Outside, away from the front door, she rings 0800 111 999. Cadent: "Once you're safe, call".¹ Going outside to be safe is this course's reading of that line.
6. The wait. Nobody goes back in until the engineer has given the all-clear, and she lets the engineer in when they arrive (Cadent).¹

Who calls? Cadent and National Gas tell the person who smells gas to call.¹² What they do not add is SSE Airtricity's "Never leave it to anyone else to call the Emergency number", or Con Edison's and Atmos's warning not to assume someone else has called.³⁵⁷ So Isla makes the call herself. Not leaving it to a flatmate is this course's reading, drawn from those three, not from a British page. The gas then stays off until the emergency engineer says otherwise.

The job labels from lesson 1 fit this without strain. Turning the valve is Yours, on conditions: in Great Britain or Northern Ireland, if neither the smell nor the meter is in a cellar or basement, and, this course adds, if you can reach it without going further into the smell. The call is Yours. Everything to do with the leak after that belongs to the emergency engineer.

A split-level house in Connecticut, with a gap for you

Now the wrinkle, in the US. The Okafors live in a split-level house in Connecticut. On a Sunday morning their teenage son smells gas on the lower level, where the meter and the furnace are. A cousin visiting from England says: "Go down and turn it off at the meter, then open the windows. That's what we do at home."

The cousin's steps are Great Britain's, and this house is in Connecticut. This is how the US sources read it.

1. Nobody goes down. None of the US leak pages read tells a householder to turn the meter, and SoCalGas says "DO NOT attempt to control the leak".⁶ The windows stay as they are: none of the three utilities says to open them.
2. Everyone leaves, now. Con Edison's first instruction is to leave and take everyone, even if the smell isn't strong.⁵ The son doesn't stop to switch the lower-level light off, and nobody picks up the kitchen phone or rings the next-door bell on the way out (Con Edison's list).⁵

The cousin's advice is Great Britain's, from British gas networks. In Connecticut, the advice to follow is the Okafors' own gas utility's. This course did not read it, but the three US utilities it did read all start by leaving, which is why the callout splits by country.

The labels, in the US: the meter valve is Call someone on every leak page read, the utility's to deal with and not yours, unless your own utility's page tells you otherwise. The call is Yours, from a safe place.

What people get wrong

"Switching the lights off makes it safer." It feels like making things safe. Cadent and National Gas say not to turn switches on or off, and Con Edison gives the reason, sparks.¹²⁵

"No smell, no leak." The smell is the warning you've been told to expect, so its absence feels like an all-clear. A lost sense of smell and odour fade can both hide a leak, SoCalGas and Con Edison say, though Atmos calls fade in the gas rare. Listen and look as well.⁵⁶⁷

"If the meter's in the cellar, just be quick." It feels like the fastest way to stop the gas. Cadent and SSE Airtricity say don't go into a cellar or basement with a leak in it, and get out of the building; National Gas says not to turn off at the meter if the meter is in the cellar. None of them gives a reason.¹²³

"Ringing the neighbours' bells is the responsible thing." In the US, Con Edison lists ringing a doorbell among the things not to do; take people with you instead.⁵

"Someone will have called by now." When several people can smell it, each can assume another has rung. SSE Airtricity, Phoenix, Con Edison and Atmos all say not to assume it or leave it to anyone else.³⁵⁷⁸

"The UK steps and the US steps are the same thing in different words." They differ at the first move. Follow your own country's.

Practice

For your plan

This lesson adds to the emergency card: the full leak steps for your country, with the number, beside lesson 1's burst-pipe order. It adds to the map: the meter, which way the valve handle lies, and whether it's in a cellar or basement. And it adds to the stop list: in a leak, every switch and flame; in Great Britain, going back in before the engineer's all-clear; and in the US, bells and phones inside, and the meter unless your own utility tells you otherwise.

Connections

Lesson 1, "How a house works, and where it switches off", found the valve and set out the job labels, and this lesson used them on the night itself. Lesson 5, "Electricity: what trips, and why", passed on a US utility's advice to stand to the side when resetting a breaker in case it arcs; the "no switches" line in a gas leak is a worry about the same kind of spark, in a room where it matters more. Lesson 7, "Heating: boilers, radiators and furnaces", stopped at the boiler's casing. Next, lesson 10, "Gas: the law and the engineer", reads the law behind that line, what the user instructions leave to you, and how to check an engineer's card. Then lesson 11, "Carbon monoxide and the alarms that warn you", takes up the gas you cannot smell at all. The response to carbon monoxide poisoning is First Aid and CPR lesson 14's, and is not retaught here.

Go deeper

• Cadent, "What to do if you smell gas", free, read here in full. Cadent's steps for its own network, with its page on finding your meter linked from it.
• SoCalGas, "Natural Gas Leaks", free, read here in full. Odour fade and the signs to see and hear, written for the utility's own customers.
• Con Edison, "Gas Safety", free, read here in full. The one page read that gives the reason for the "don't touch" list.

Sources

1. Cadent Gas, "What to do if you smell gas", "Locating your meter and turning off the gas" and its homepage for the area it serves. Read: full text of the first two; re-read on the live pages 25 and 26 September 2026. About Cadent's own network: the North West, the West and East Midlands, the East of England and North London.
2. National Gas, "Emergency Contacts". Read: full text; re-read 25 and 26 September 2026. Great Britain; its guidelines "apply to all gas users".
3. SSE Airtricity Gas Supply NI, "In an Emergency". Read: full text; re-read 25 and 26 September 2026. One of Northern Ireland's gas suppliers.
4. Health and Safety Executive, "Gas safety: home owners". Read: full text; re-read 25 and 26 September 2026.
5. Con Edison, "Gas Safety". Read: full text; re-read 25 and 26 September 2026. A New York utility, about its own customers.
6. SoCalGas, "Natural Gas Leaks". Read: full text; re-read 25 and 26 September 2026. Page stamped 23 July 2024. A US utility, about its own customers.
7. Atmos Energy, "Recognizing a leak". Read: full text; re-read 25 and 26 September 2026. A US utility, about its own customers.
8. Phoenix Energy, "In an Emergency". Read: full text, 26 September 2026. A Northern Ireland gas network company, about its own engineers.
9. SoCalGas, "Emergency Preparedness". Read: full text, 26 September 2026. Page dated 16 July 2024. Earthquake and emergency advice for the utility's own customers.