Asbestos in fireplaces and stoves: seals, protective boards and flue connections

In a fireplace or stove, asbestos is mainly found in the seals of doors and glass panels, in the protective boards behind and around the fireplace, in the sealing compound at the connection between the flue pipe and the chimney, and in mortar used for repairs. Ordinary bricks and stones are generally not under suspicion; the materials between and around them are. If an open fireplace, tiled stove, wood-burning stove or wood-fired cooker was installed or repaired before asbestos was banned (2005 at the latest across the EU, and earlier in many countries), it is worth having the parts you plan to remove analysed in a laboratory before you touch them, because asbestos cannot be identified with the naked eye.

Which parts of a fireplace can contain asbestos?

Asbestos was used as a heat-resistant material and was therefore used precisely where fire, hot flue gases or hot surfaces meet the rest of the structure.

Door and glass seals

The rope seals of the firebox door, the ash pan door and the cleaning openings, as well as the seals of the viewing glass, are the most common suspected asbestos in a fireplace or stove. An old seal is often a grey or white braided rope that has become hard or brittle from the heat. Today's replacement seals are asbestos-free but can look exactly like the old ones, so appearance decides nothing.

Protective boards behind and around the fireplace

Behind a wood-burning stove, wood-fired cooker or open fireplace, boards were often fixed to the wall, and sometimes the floor, as fire protection. A hard, grey board may be asbestos cement. A light, softer insulating board that scratches easily is a more delicate material, because it can create dust just from being handled. The board may be painted, tiled or hidden behind a metal sheet. You can read about fireproof boards elsewhere in the building in the article Asbestos in fire protection.

Connection between flue pipe and chimney

The flue pipe of a wood-burning stove or wood-fired cooker is connected to the chimney through an opening in the masonry, and the connection is sealed with rope, compound or mortar. Old fire-resistant sealing compounds and rope seals may have contained asbestos. Ventilation ducts and pipes were also made of asbestos cement, so a grey, cement-like pipe at the chimney connection should be tested as a separate sample.

Mortar and repair compounds

Over the decades, fireplaces were patched, plastered and repointed. Fire-resistant mortar, plaster and jointing compound from repairs may date from a different period than the original masonry and may have contained asbestos. Asbestos was sometimes added to mortar and plaster for indoor use, so with a tiled stove it can make sense to test the joints and mortar as well.

Internal parts of the fireplace

In older stoves, such as bread ovens and sauna stoves, asbestos millboard was used as fire protection and may sit inside the fireplace or between its components. It usually only comes to light when the fireplace is opened up, repaired or demolished.

When is it worth testing the fireplace?

An intact seal or board that nobody touches does not release fibres. With a fireplace or stove, the risk is usually linked to maintenance and repair, when old material is torn out, scraped off or broken. Test the material before the following work:

• replacing the door or glass seal, when the old seal is torn out and the groove cleaned
• replacing a wood-burning stove or wood-fired cooker and disconnecting the flue pipe from the chimney
• replacing a fireplace insert or demolishing an open fireplace
• removing a protective board, drilling into the board or fixing new cladding on top of it
• rebuilding a stove or chimney, new plaster or repointing a tiled stove
• demolishing the entire fireplace or chimney as part of a larger renovation

Heat and long use make seals and soft boards fragile. A crumbling seal or a dusty board is a reason to be especially careful even before the actual work begins.

Where on the fireplace do you take the sample?

• Take a separate sample of each material that looks different: seal, board and compound separately. Then you know which part must be treated as containing asbestos.
• If the fireplace has several doors and their seals look different or were replaced at different times, test them separately.
• Take the board sample from an edge or corner so that the layers on the board, such as paint, mortar or tiles, come with it.
• Take the sample of compound or mortar at the spot you plan to demolish or repair.

How many samples are needed is described in more detail in the article How many asbestos samples are needed?.

How to take a sample from a fireplace

1. Make sure the fireplace has cooled down completely and there are no embers left in the ash.
2. Wear disposable gloves and a respirator of at least class FFP3.
3. Lightly moisten the sampling spot with a spray bottle to keep dust to a minimum.
4. From a seal: use a sharp knife to cut off a piece of about 2–5 centimetres, for example at the bottom edge of the door or at a spot where the seal has already come loose. Do not pull the whole seal out of the groove.
5. From a board: use a chisel or knife to remove a piece of about 2–5 centimetres from the edge of the board so that all layers through the board come with it.
6. From compound or mortar: use a chisel to remove a small piece at the connection or repair, through the full thickness of the layer.
7. Put each piece in its own resealable plastic bag, seal it and place it in a second bag.
8. Label the bag with the fireplace and the part, for example "Living room, wood-burning stove, firebox door seal".
9. Cover the sampling spot with tape and wipe the area with a damp cloth.

Once you have taken a sample of the door seal, the door may no longer close tightly, so do not light the fire again until the seal has been replaced. If the board or seal crumbles in your hands or creates dust, do not take the sample yourself but leave the sampling to a professional. You will find general advice on tools and packaging in the article How to take an asbestos sample.

What does the result mean for the fireplace?

Semlab analyses the sample with a JEOL SEM-EDS electron microscope in accordance with ISO 22262-1, and you receive the result by email in English, usually on the same day the sample arrives at the laboratory. The result shows whether asbestos was detected in the sample you sent.

• No asbestos detected: the result applies to the part that was sent as a sample, for example the seal of one door or the board behind the fireplace. The other parts of the fireplace are tested separately.
• Asbestos detected: that part is treated as containing asbestos. Replacing the seal, removing the board and demolishing the fireplace are planned as asbestos work under the occupational safety rules, and the demolition is carried out by a contractor specialising in asbestos removal.

If the fireplace is part of a larger renovation or demolition that requires an on-site asbestos survey, a qualified surveyor carries out the survey on site. Semlab is a laboratory and does not carry out on-site surveys.

How much does analysing a sample from a fireplace cost?

The analysis costs €49.99 incl. VAT per sample, and the price is the same for 1–100 samples. For orders of more than 100 samples we can make a separate arrangement. Postage is not included in the price. If you have the seal, board and connection compound of the same fireplace tested, that is three samples. You can order the analysis online, pay by card and send the samples as a letter or small parcel with your national postal service to the laboratory in Finland.