Flues in Voids FAQ's


Why is carbon monoxide (CO) dangerous?

CO is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon‐based fuels, including gas. It is only when the gas does not burn properly that dangerous levels of CO are produced. CO stops the blood from bringing oxygen to cells, tissues, and organs and can kill quickly. Around 20 people in Great Britain die each year from CO poisoning caused by faulty gas appliances and flues.

CO poisoning can easily be confused with food poisoning, viral infections, flu or tiredness. Symptoms to look out for include headaches, breathlessness, nausea, dizziness, collapse, loss of consciousness, tiredness, drowsiness, vomiting, pains in the chest, stomach pains, erratic behaviour or visual problems.

What should I do if I experience any symptoms of carbon monoxide poisoning?

  • Get fresh air immediately. Open doors and windows, turn off gas appliances and leave the house
  • See your doctor immediately or go to hospital - let them know that you suspect carbon monoxide poisoning. They can do a blood or breath test to check
  • If you think there is immediate danger, call the Gas Emergency Helpline on 0800 111 999
  • Get a Gas Safe registered engineer to inspect your gas appliances and flues to see if there is a dangerous problem

If there is an immediate safety issue, why have I got two years to fit inspection hatches?

Getting the work completed may take time, especially if you are contacting your builder or home warranty provider, or you may be waiting for your next scheduled boiler service. By getting your boiler serviced by a Gas Safe registered engineer and fitting audible CO alarm(s), to BS EN 50291:2001, you are helping to manage any risk until the inspection hatches have been installed.

Why are hidden flues an issue?

Advances in technology allowed boilers to be put in a greater variety of positions, not just on an outside wall, suiting the development of flats and apartments where space was at a premium. This resulted in some boilers being installed in a way that the flue cannot be inspected to make sure it is correctly fitted and safe.

Do I have to get inspection hatches by law?

No. There is no legal duty on the consumer to have inspection hatches installed. However, there is a long-standing legal duty on gas engineers to be able to visually check the flue to ensure it is safe. In the majority of cases this will be only be possible though the installation of inspection hatches. If gas engineers cannot view the flue along its length they will advise you from January 2013 that the installation is ‘At Risk’ and will seek your permission to turn it off.

If I am safe to use my boiler until 31 December 2012 with CO alarms and boiler checks why must I have inspection hatches installed at all?

Gas engineers are required to be able to see the flue to inspect it. In the majority of cases, unless inspection hatches are fitted, they cannot confirm that your flue is safe and will ask your permission to turn the boiler off. Having your boiler serviced and the fitting of CO alarms are only being allowed as a short‐term measure to help you manage the risk until inspection hatches have been installed. They are not an alternative to having access to the flue.

How much will inspection hatches cost me?

It will vary from property to property. It is recommended that hatches are at least 300mm x 300mm and wherever possible, be positioned within 1.5m of any joint in the flue system. Therefore, some properties will only need one hatch, while others may need more

Basic inspection hatches must comply with the Building Regulations and are likely to cost from £75, though you may choose to fit more expensive ones for cosmetic reasons. Costs for the fitting of the inspection hatches will be extra.

Why didn’t my gas engineer raise this issue when they visited last time?

If your flue could not be inspected, your gas engineer should have informed you on a previous visit that your system was ‘Not to Current Standards’, unless there was evidence of an additional safety issue that would have required your boiler system to be declared ‘At Risk’ or ‘Immediately Dangerous’.

Technical instructions to gas engineers changed from January 2011 following a number of cases where, once inspection hatches had been installed, faults were found in flue systems. There have also been several cases where CO from a faulty boiler has been found to be entering properties from faulty flues that are concealed within voids.

In light of this evidence, industry organisations have now decided it is right for gas engineers to classify installations with concealed flues as ‘At Risk’ for the safety of the occupants.

What does ‘At Risk’ mean? Can I still use my boiler?

If your system is ‘At Risk’ it could become dangerous in the future. Having inspection hatches installed, which allow for the flue to be viewed along its length, will mean your system is no longer classified ‘At Risk’ (as long as there are no additional safety issues found with the boiler or flue system).

If inspection hatches to allow the flue to be seen are not fitted by 1 January 2013, your gas engineer will advise you that the installation is “at risk” and turn the boiler off, with your permission. As an interim measure, to allow time for the necessary work, a registered gas engineer can carry out safety checks and ensure that audible CO alarms (meeting BS EN 50291:2001) have been fitted.

I think I have a home warranty but don't know who it is with.

When you purchased the property your solicitor should have told you who was providing the home warranty. It is possible that you have correspondence from the warranty provider. The main warranty providers in the UK are NHBC and Premier Guarantee. Depending on the age of the property Zurich Building Guarantee may have provided the warranty. The contact details for these are listed in the associated Safety Notice.

My home warranty has expired. What does that mean for me?

If your home warranty has expired, you or your landlord will have to meet the cost of the inspection hatches and any defects to the boiler or its flue. If you receive benefits you may be entitled to financial assistance. Further details can be found on the Health and Safety Executive website.

It may still be worth contacting your home builder who may be willing to assist in some way, or be able to recommend reputable building services companies to carry out the work.

Where do I get CO alarms and what will they cost me?

Some we recommend are;










CO alarms can continue to be used once inspection hatches have been installed and are recommended as an additional precaution.

Who do I approach to install inspection hatches?

A competent builder or building services company should be able to fit the inspection hatches. The builder will need to speak to a registered gas engineer on how many inspection hatches are needed and where they should be located.

If you do not know a builder, the government supported ‘Trustmark’ scheme should be able to provide advice on how to find a reputable building company to carry out the work. Go to trustmark.org.uk or phone: 01344 630 804 for further details.

Do I need to fire-rated inspection hatches?

It is possible that the original plasterboard ceiling will have been designed to provide fire protection; it may also provide acoustic/noise protection too. The hatches that are fitted need to provide equivalent fire/noise protection to the ceiling they are replacing. Fire-rated hatches are more expensive than non-fire rated budget ones. When retro-fitting inspection hatches it is recommended that hatches rated to provide a minimum of 1-hour fire resistance should be specified. Non-fire rated hatches should only be fitted where professional advice has confirmed they are suitable - such advice may be available from the original builder or a suitably qualified surveyor. [Note: Where advice is not freely available from the original builder it may well be cheaper to fit 1-hour fire-rated hatches than to pay for professional advice to determine whether or not they are required.]

‘Inspection hatches installed to provide access to an existing chimney system in a void in the majority of cases should usually have a minimum of one hour fire resistance for residential buildings with floors no higher than 18m above ground level. The use of non-fire rated hatches needs to be assessed by a suitably qualified surveyor to ensure satisfactory fire and acoustic resisting performance. The following bullet points may provide additional help in determining the type of inspection hatches you may need:

  • Two storey houses and those with fire escape stairs require robust fire resisting floors and escape routes that usually rely on the internal linings to maintain integrity for the required length of time. A fire resisting hatch of some type will usually be required in these situations.
  • In apartments with concrete or timber floors, the plasterboard ceiling below could be providing fire resisting properties to either the structural elements or the protected escape routes. In most situations the suspended plasterboard ceiling will have been an integral part of the assessed acoustic performance, any hatches within it will need to maintain satisfactory acoustic performance. A denser fire rated hatch should provide better acoustic performance than a non-rated hatch. Therefore In most apartment block situations a rated hatch is either required or is beneficial.
  • The majority of installations would normally be covered by the above, but there may be other situations where non-rated hatches can be used. This will require an assessment from someone that is suitably qualified and understands the technical aspects of the building.

In all cases the inspection hatch manufacturer will be able to confirm the fire resistance and provide a fire test certificate. In new build situations, the building control body will be able to advise on the suitability of the inspection hatches.

What if I don’t have inspection hatches fitted?

From 1January 2013 gas engineers can continue to work on your boiler but should advise you that it is “At Risk” and will ask your permission to turn it off, to ensure they comply with industry guidance. If you choose not to fit inspection hatches, you should however continue to have your boiler maintained every year by a Gas Safe registered engineer.

What if I refuse the gas engineer permission to turn off my boiler?

The aim of this guidance is to make consumers aware of important safety issues relating to hidden flue systems and carbon monoxide and to set out what action should be taken to protect those who live in or visit the property. As a consumer you are free to refuse the gas engineer permission to turn off your boiler. In these circumstances however you will be asked to sign paperwork to confirm you accept responsibility for those defects identified in the system which could result in a serious incident.

Who do I approach to install inspection hatches?

A competent builder or building services company should be able to fit the inspection hatches. The builder will need to speak to a registered gas engineer on how many inspection hatches are needed and where they should be located.

If you do not know a builder, the government supported ‘Trustmark’ scheme should be able to provide advice on how to find a reputable building company to carry out the work. Go to trustmark.org.uk or phone: 01344 630 804 for further details.