How many asbestos samples do you need?

You take an asbestos sample from each different material or layer build-up that will be removed, sanded or drilled during the renovation. The number of samples does not depend on how many rooms or square metres are affected, but on how many different materials, layer build-ups and repairs from different periods there are in the work area. For renovating a single wall or floor, one sample is often enough, while stripping out an entire apartment usually requires several.

Here we show how to work out the number of samples, when one sample covers a large area and when you should take separate samples even of materials that look the same.

Basic principle: one sample per material unit

The laboratory analyses what is in the bag. The result applies to the sampling location and to the same material, i.e. the same product installed at the same time. The number of samples therefore depends on how many different material units there are in the work area. A separate unit is:

• A different material: vinyl floor covering, tile adhesive, wall filler, pipe insulation and asbestos cement sheet are each separate samples, even if they are in the same room.
• A different layer build-up: tiles laid in a mortar bed and tiles laid in adhesive on filler are different units.
• A different installation date: material from the original construction and material from a later renovation are different products, even if they look the same. Repairs are also often made with a different material from their surroundings.
• A different part of the building: material that looks the same is still examined separately if, for example, it is found both in a wet room and in a dry room.

Area alone does not increase the number of samples: if two bedrooms have the same vinyl floor covering laid at the same time, one sample is enough for both. The layers of the same building element, for example tile, mortar and adhesive, are sent as one sample so that no layer goes unexamined.

How to work out the number of samples step by step

1. List the work. Write down what you intend to remove, sand, chisel off or drill. If you only paint a whole surface without sanding or scraping, the old layers are not disturbed.
2. Check what each task will break open. The layer build-up can often be seen at a damaged spot or behind a skirting board.
3. Group what is the same. Group together areas where the material looks the same, is laid in the same way and probably dates from the same renovation.
4. Separate what is different. Repairs, a different colour or pattern, a different substrate, a different part of the building and a different renovation phase are reasons for a separate sample.
5. Take one sample from each group. Number the bags and note which area each sample represents, for example "S1 kitchen, floor, vinyl floor covering and adhesive". Use the same name in your order so that each result is matched to the right location.
6. If in doubt, take one more sample. It is cheaper to have both materials analysed than to have to interrupt the removal work later.

When is one sample enough for a large area?

When the material is uniform: the same appearance, the same substrate and the same installation date across the whole area. This could be, for example, the floor covering of a room, the tiles on a wall or a uniform ceiling filler. Take the sample at a spot that is typical of the whole area, not in a repaired corner, for example. If you are only drilling fixing holes in a tiled wall, one sample of the layer build-up of that wall is enough.

When should you take several samples of material that looks the same?

• The building was renovated in stages. The vinyl floor coverings in the hallway and kitchen may look the same but come from different decades.
• The area has been repaired. A repaired spot was often treated with a different filler or adhesive.
• There is an old surface under the new one. A hidden old floor covering or old tiles belong in the sample. If the layers are removed separately, you can also take separate samples of them.
• Different apartments are involved. In an apartment building, the surfaces of the apartments may have been renewed at different times, so the result for one apartment cannot be applied directly to the next.

Worked examples

The numbers below show how to work it out and are not fixed rules: the right number depends on what your particular renovation will break open.

• Bathroom: if the walls have one type of tile and the floor another, this example gives two samples, each with all layers. A ceiling filler that is to be sanded is a third sample, and partly replaced tiles are examined separately. See also Asbestos in the bathroom.
• Kitchen: the vinyl floor covering with adhesive, the tiles between the cabinets and a wall that is to be opened up give three samples in this example. If the same floor, laid at the same time, continues into the hallway, one floor sample is enough for both.
• The floors of the whole apartment: the same covering laid at the same time in all rooms can mean a single sample. If the hallway has a different covering, the kitchen vinyl floor tiles and the bedrooms a vinyl floor covering, that makes three samples.
• Larger renovation of a house: an older house can contain materials from many decades, for example pipe insulation in the basement, asbestos cement sheets on the facade or roof and fillers and floors inside. The number of samples follows from the list of materials, so it can be ten samples or more. Before extensive removal work, an asbestos survey may be needed.

Do not mix different materials in the same bag

If pieces of floor covering, wall filler and tile adhesive are in the same bag, a positive result does not show which of them contains asbestos, and then all of them have to be treated as asbestos-containing. A sample should represent only one material. So pack each material in its own bag and keep the layers of the same building element together.

Sampling in brief

1. Wear disposable gloves and at least a class FFP3 respirator.
2. Moisten the sampling spot with a spray bottle.
3. Remove a piece of about 2–5 centimetres through all layers down to the substrate.
4. Put the piece in a resealable bag and that bag inside a second bag.
5. Write the sample number and sampling location on the bag.
6. Cover the sampling spot with tape and wipe the area with a damp cloth.

More detailed instructions are in the article How to take an asbestos sample.

What does the result show if you send several samples?

Semlab analyses each sample separately with a JEOL SEM-EDS electron microscope, and the report contains one result per sample. You receive the report in English by email on the same day the samples arrive at the laboratory. Each result applies to the material group that the sample represents, so clear numbering is just as important as the sample itself. If asbestos is detected in a sample, read on in the article Positive asbestos result.

How much does analysing several samples cost?

The analysis costs €49.99 incl. VAT per sample, and the price per sample is the same however many samples you send. Three samples therefore cost 3 × €49.99 = €149.97 incl. VAT. Postage is not included. You can order the analysis online, pay by card when you order and post all the samples together as a letter or small parcel with your national postal service.