The toxicity of smoke is an important parameter when you are caught in a fire. Therefore, there are strict requirements for what the smoke from materials in trains and ships may contain. The same rules, however, do not apply to building materials or the largest source of smoke in our homes – our furniture.
As is well known, in the right quantities, everything is poisonous. And the quantities may be comparatively small when it comes to substances in smoke. If you are in a place where smoke is a crucial factor in case of fire, for example, a ship, plane or train, the toxicity of smoke is an important part of the materials’ fire-safety properties.
- The interest in toxicity in smoke grew after the fire on the Scandinavian Star ferry in 1990, where many of the ship’s passengers died due to toxic smoke, says Lina Ivar Andersen, Bachelor of Engineering and specialist in chemistry at DBI, the Danish Institute of Fire and Security Technology.
The disaster prompted the International Maritime Organization (IMO) to prepare new rules in the area, and today there are also requirements for smoke in materials for planes and trains.
- Especially for trains that are to travel through tunnels, where the risk of being poisoned in a fire is even greater, there are strict requirements regarding the toxicity of smoke. The more difficult it is to escape from a fire, the more important the smoke’s toxicity is, says Lina Ivar Andersen.
When flame retardants are a problem
There is no limit to how many substances there are to test when you investigate the toxicity of smoke, but typically the substances that are most poisonous and have resulted in death are measured – this typically includes carbon monoxide, hydrogen sulphide, nitrogen oxide, hydrochloric acid, hydrogen bromide, hydrofluoric acid and prussic acid. These substances are especially found in smoke from artificial substances, such as fibreglass or plastic materials, and may be fatal even in small doses.
- Therefore, it is a question of using sufficiently small amounts of these materials in a product. The flammable decorations on non-flammable steel walls on ships are, for example, very thin. Nearly all materials can cause problems with regard to the toxicity of smoke if there are too many of them, says Lina Ivar Andersen.
It can be a challenge when a product has to live up to toxicity requirements. Not least because other, good fire-safety properties may increase the toxicity of a product. Low heat development and fire spreading are also good properties, and they can be achieved by using flame retardants in the product.
- Flame retardants often work by making the product smoulder instead of burst into flame. On the other hand, this means that more smoke develops and the toxicity becomes higher than if it did actually burst into flames. Often, the use of more fire retardants results in more smoke and toxicity. These are useful tools, but their use is a difficult balance for manufacturers, says Lina Ivar Andersen.
No requirements for building materials
The toxicity of materials is not just a parameter for transport. And although its application to building materials is not on our doorstep, it is sometimes a topic that is discussed in European forums. Recently, the European Commission investigated the need for regulating the toxicity in smoke from building materials, which resulted in the publication of a report in the autumn of 2017. It showed, among other things, that it is probably not building materials that comprise the greatest risk for emitting poisonous smoke in our buildings and homes. On the contrary, it is the things we fill them with.
- The smoke from materials that we normally build with presumably contain a limited amount of toxicity. On the other hand, we fill our homes with furniture containing many foam materials, which give off much more toxic smoke, says Lina Ivar Andersen.