DIY and gas safety
Wrong actually. Even placing a bookcase or floorcushion in the wrong place (blocking up that pesky vent in the living room that lets in such an icy draught in winter that you've got to have the gas fire on permanently) or fitting a door in the doorway that unaccountably had its door missing when you moved in, fitting an extractor or cooker hood in the kitchen, getting an extension or conservatory built, or building a side and end wall to an existing car port — all these could lead to you waking up dead one morning as happened to a local woman recently (or, perhaps even more horrifically, finding one's children dead as in the case in Corfu in 2006).
Why? In the examples above:
- Putting up the kitchen unit covers a vent that supplies air to an old boiler with a conventional flue that gets its air from within the room it's installed in. Normally the boiler's Products Of Combustion (POCs) comprise mainly harmless carbon dioxide (CO2) and water (H2O) as steam, and these gases, being hot and lighter than air, rise up the boiler's flue (or chimney) and out of the house. Fresh air is drawn into the room from the air vent to replace the gases exiting up the flue. If the supply of fresh air is restricted (by blocking the vent) the POCs aren't taken away but stay in the boiler's combustion chamber where the boiler converts some of the CO2 to deadly carbon monoxide (CO), which spreads throughout the room.
- In the second example the pesky vent is supplying combustion air for the back-boiler behind the gas fire. Cutting off the air is likely to result in CO production and the CO entering the room.
- The missing door in the third example was between the conventional-flued boiler in the kitchen and its only source of ventilation in the pantry next to the kitchen, and had presumably been removed to prevent this ventilation being stopped by the door being shut.
- An extractor fan or cooker hood (extracting to outside rather than recirculating) in the same room as a conventional-flued appliance can suck air away that the appliance needs for proper combustion as well as sucking products of combustion — including CO — into the room rather than allowing them to go up the flue.
- An extension or conservatory built onto the side of a house changes the ventilation to rooms that formerly had outside walls and windows. Again this can reduce ventilation for conventional-flued appliances in these rooms and, in the case of kitchens containing gas cookers, these must generally have ventilation direct to outside so if the kitchen becomes an inside room additional ventilation is required.
- A room-sealed boiler flue discharging under a car port which has 3 open sides is OK, but if the sides are closed the boiler's fumes are likely to build up rather than dissipating within the enclosed car port area. Since the boiler's air intake is adjacent to its flue outlet the fumes will re-enter the boiler which will burn some of the CO2 it has produced to create a high level of CO in its flue gases, which can enter the house via windows, air vents and air-bricks.
Some of the examples above, such as the missing door, may seem contrived but I have come across them (though thankfully not with dangerous attempts to "rectify" the situation).
Conventional Flue appliances
Most of the examples involve (generally) older conventional-flued appliances: generally floor-standing boilers, and back-boilers with gas fire fronts in fireplaces. These should in any case be serviced annually to clean out lint filters inside them and check that they're burning properly, and a Gas Safe-registered engineer should check that ventilation is provided for the appliance and check that the flue is drawing properly, and should spot possible hazards such as the examples above.
Even so a dangerous situation can arise long before an annual service picks it up so it helps if everyone knows the basic dangers involved in such appliances, in the same way that everyone should know that if you smell gas you open doors and windows and don't strike a light! In a nutshell, if you've got a conventional-flued boiler, think: "where does it get its combustion air from?". There should be a ventilator — often an air-brick on the outside wall, the size of a house-brick or two — allowing air into the room with the boiler. On the inside wall there may be a vent grille but it mustn't be closable (or blockable) and mustn't have any sort of fly-screen inside. Get the boiler serviced annually. Really. Replace it as soon as you can afford to: it's probably only about 65% efficient averaged over a year (SEDBUK rating) whilst a new one will be about 90% efficient, which at current gas prices and interest rates could pay back its replacement cost and provide a return on the investment in the form of saving on fuel bills in years to come — as well as giving peace of mind on the safety front. In any case such an old boiler may not have a lot of life left in it, and is likely to be unreliable, requiring thermocouple changes and other repairs from time to time (possibly at the most inconvenient — and expensive — times) as well as more (and therefore more expensive) maintenance; so it makes sense to replace it sooner, when you choose and can arrange a reasonable price for the work, rather than later when it actually packs up for good and you have to pay, possibly over the odds, for an emergency replacement.
The inherent vulnerability of conventional-flued appliances like this to the sorts of risks described above is one reason why new boilers, at least, are rarely found with this sort of flue arrangement. They are either "room-sealed", drawing air in from outside and discharging POCs back outside, usually through the same concentric flue; or have fan-driven conventional flues and oxygen-depletion sensors so they are much less likely to produce CO from inadequate ventilation.
The other type of appliance particularly liable to kill by Carbon Monoxide production is gas fires. Often these are installed into fireplaces with chimneys which can get blocked by birds either falling down the flue or building nests in the chimney pot in summer when the fire's not in use. Gas fires should also be serviced annually. Really.
Other gas-safety related DIY issues
What about repointing, rendering or pebble-dashing an outside wall? Harmless enough it might seem, but rendering or pebble-dashing might block a ventilator for a gas appliance. And repointing, rendering or pebble-dashing a wall which has an exposed gas pipe (maybe from an external meter box running along or below the box before entering the building) can bring the pipe into contact with cement products which can cause corrosion to copper pipe resulting in it eventually leaking. Although at least the leak would be outdoors. DIY/building work inside the house resulting in gas pipes being placed in contact with cement could result in leaks internally! In either case the damage could take years to occur and start with a small persistent leak which could build up dangerously in some inaccessible space.
Another point to watch with gas pipes running through walls (especially where a pipe from an external meter enters the house) is that it should be run in a plastic or metal sleeve and the gap between pipe and sleeve should be sealed on the inside only. The enthusiastic re-pointer, or someone rendering or pebble-dashing, may block up the gap between pipe and sleeve on the outside, not only bringing the pipe into contact with possibly-corrosive cement but preventing any leakage discharging to outside air.
Is it legal to do your own gas work?
This question — and related ones such as what specifically counts as gas work (fixing a boiler onto a wall? installing pipework for gas but not yet connected to a gas supply?) — arouse heated debate.
CORGI (used to) imply, without actually saying specifically, that it is illegal. In fact the law — the Gas Safety (Installation and Use) Regulations 1998 (GSIUR) — says (Section 3 para 1) that anyone who does gas work must be 'competent' (which it doesn't define). It further says (Section 3 para 3) that anyone doing gas work as an employed or self-employed person must be Gas Safe registered
This appears to allow genuine DIYers to do their own gas work — provided they are competent. The difficulty for the conscientious DIYer is that they may be competent at the various physical tasks (e.g. pipe fitting) and follow the manufacturer's instructions in what they are doing, and have test kit such as a manometer (and know how to use it) but may lack some other knowledge necessary to carry out a gas-related job safely, and not even know that they lack that knowledge, so are not really competent. For example apparently straightforward tasks such as installing a gas hob or even replacing a free-standing ("slot-in") cooker involve a few factors (can one use a flexible hose? what about an isolation valve? stability device? ventilation requirements? how to check safety devices?) which may not be obvious to the DIYer, or covered in the manufacturer's instructions.
I expect that in practice whether a DIYer was competent would probably be decided in court if something went wrong, e.g. if an appliance they had worked on was subsequently found to be dangerous and the case was reported to the Health and Safety Executive who decided to prosecute. At this point the DIYer might be asked various questions to see how much they understood of what they were doing. This might include questions on what sort of pipe fittings are suitable for gas work, how much and what sort of ventilation needs to be allowed for the appliance, how to test for gas soundness and correct operation of flues, and so on.
I am sure there are some truly expert and well-informed DIYers who do competently maintain and install their own appliances, and probably do so pretty well. One also hears of professional, supposedly competent, installers who do incompetent work — either an occasional slip-up or consistently badly. (Hopefully in the latter case they are sooner or later either made to get up to standard or de-registered.) To say that a DIYer should never do any gas work and always call in a Gas Safe engineer is politically correct, but one can imagine that a skillful and careful person might replace a failed thermocouple on a properly-serviced boiler on Christmas Eve with a degree of care and workmanship that an emergency heating engineer in a hurry with a couple more jobs to get to and a family to get home to, might not.
In practice many DIYers (or unregistered plumbers or builders) who want gas appliances installed agree a course of action with a Gas Safe-registered installer where the DIYer does certain parts of the work and the installer does other parts. As an installer I want to be involved before the DIYer embarks on the work, to agree who does what and how, rather than being asked to "come in and connect it up". I would not, for example, be happy to put my name (and expensively and laboriously acquired Gas Safe registration, not to mention anyone's safety) on the line by commissioning a boiler which I didn't know was securely fixed to the wall, or pipework that might have been made with the wrong type of (corrosive) flux which could eat through the copper in years to come — points which the DIYer asking me to commission an appliance might not appreciate.
In the case of installation of a gas appliance there is also the issue of Building Regulations: installation of "heat producing" appliances is "notifiable" (Approved Document J) so the local authority's Building Control department must be involved. Either a building notice must be submitted (and a fee paid) and the Building Control Officer (BCO) will inspect the work and issue an appropriate notice to say the the installation complies with regulations, or a "competent person" (such as a registered installer) who installs an appliance can "self-certify" their work. Either way the householder ends up with a notice showing that the installation complies with building regs, which they may have to produce for the buyers (or their solicitors) when selling the house.