Fume Extraction

What is a fume?

In the world of fume extraction, we define a fume as: A vaporised solid particulate that has condensed.

In the simplest terms, a fume is created when a solid material is heated up or burnt to the point the solid particles become “vaporized” i.e. become a vapour or a gas and then condense into a visible plume, although a vast majority of the fume you can’t see with the naked eye.

The simplest example of a fume is smoke. When you burn something like wood, it heats up to the point that a visible and odorous plume erupts from its surface. Wood smoke is an instantly recognizable smell.

Other examples of this also include a fume from laser cutting where the laser vaporizes the material it is cutting or a solder fume, which is caused mainly by the flux being melted.

Fumes require applied heat in order for them to be created and as result the hot air and particles automatically rise up from the source. Fumes also contain a degree of vapours and gases but are mostly made of solid particles.

What is a vapour?

For the purposes of extraction, we define a vapour as: The gaseous phase of a substance which is normally a liquid or solid at room temperature. It behaves as a gas.

The big difference between a vapour and a fume is that vapours contain no solid particulates at all. This means that usually they can’t be seen by the naked eye but in dense enough clouds it can be tasted and as they condense back into their normal state, they may leave a residue.

Most vapours are generated by a liquid under going natural evaporation or by being heated to stimulate evaporation. A great example if this is Isopropanol Alcohol (IPA). IPA is a commonly used product in many work places and IPA evaporates very quickly at room temperature producing a lot of vapour. IPA has a very distinctive smell and the moment the container is open IPA vapours being to pour out of it.

Vapours can also have other properties that we need to consider. They may be flammable, explosive or corrosive.

Fumes and Vapours in the work place

Some of the most common applications that produce fumes that require extraction are soldering, welding and laser cutting/ engraving (LGAC’s). These process all produce harmful fumes that require some form of extraction. There are other applications that could produce fumes and these could also need extraction. It is important to identify processes that can produce harmful fumes and how these can affect your work force. This should be done via your COSHH Assessment. Check out our COSHH FAQ’s for more information on COSHH Assessments.

Vapours in the work place are not always as obvious as they can’t be easily seen and some may not smell that much or even at all, which means people could be being exposed to potentially harmful vapours and not even know it. Glues, solvents, paints, chemicals, acids and more can all potentially give off harmful vapours.

Fume and vapour extraction

Commonly extraction solutions and systems for fumes and vapours are lumped into just fume extraction. But it is important to realise they are two different types of contaminate and thus need to be treated separately. They are also produced from different process and the way they are captured can be different as well.

Let’s look at two common applications: hand soldering and acid bathing. Both of these produce harmful contaminates that require controlling under COSHH. Both are commonly controlled by an LEV system.

Vapours

Small acid baths are commonly used to clean, strip or pickle items. It could be cleaning jewellery or precious metals or it could be for stripping fine wires of corrosion. Acid baths can sometimes be heated or can be at room temperature, either way they give off vapours that can cause harm to your health, from mild skin and soft tissue irritation to full blown corrosion, burns and permanent damage.

Typically, like many vapour producing applications, acid baths are controlled with a Fume Cabinet or Fume Cupboard (a prime example of when vapours are bundled in with fumes). Fume cabinets can be either a vented to atmosphere LEV or a recirculating LEV with carbon filters. Fume cabinets for use with acids are often made from chemical resistant materials like polypropylene as the standard metal construction may be susceptible to corrosion.

Fume cabinets are ideal for applications where the operator does not need to manipulate equipment constantly and doesn’t need to get to close to the source. They work by containing the vapours in a chamber, with access though an opening at the front of the cabinet. The vapours are then drawn out of the internal chamber and either vented to atmosphere (outside) or drawn through special carbon filters to remove the acid vapour from the extracted air and then the cleaned air is exhausted back into the immediate work place.

A vented to atmosphere LEV extracting the acid vapours work by extracting high volumes of air along with the vapours so that the acid vapours become diluted in the air stream to the point they no longer pose a risk. They can then be exhausted to the atmosphere outside.

A recirculating LEV system will draw the acid vapours through activated carbon filters. Activated carbon filters are extremely porous and have a very large surface area compared to its size. When a vapour’s particles are drawn through the carbon filters they are attracted to the surface of the carbon and chemically bonded there – becoming completely trapped. More commonly we say the vapours have been adsorbed.

Fumes

Solder fume is a very common contaminate as hand soldering is a wide spread process. Hand soldering is an intimate job, the components are usually small and require the operator to be very close. Solder fume is heated and rises directly up, normally right into the operators breathing zone.

As with vapours, fumes can be controlled by either a vented to atmosphere LEV system or a recirculating LEV system with filters. Commonly solder fume extraction uses either tip extraction (a small-bore tube mounted on the solder iron) or arm extraction (a flexible arm with a flared nozzle on that drags the fume back and away from the operator before it reaches their breathing zone.)

Tip extraction is always recirculating filters due to the high pressures needed. As with vapour extraction a vented to atmosphere extraction system works on dilution but we need to consider the solid particle content. This could cause damage to a fan and thus an inline filter is needed.

Again, much like vapour extraction, recirculating extraction with filters uses a carbon filter to remove the gas and vapour element of the fume but a HEPA dust filter is also needed to remove the solid particles.

Summary

It is important to understand that even though vapours and fumes are commonly lumped together under fume extraction, there is a subtle difference between the two and thus they are treated slightly differently when we extract them.

Fumes have a solid particulate element and are created from a heat source. Vapours have no solid particles and are created from natural or induced evaporation.

We also have to be aware that vapours can be highly flammable or corrosive and this needs to be allowed for when specifying an extraction system. Make sure you understand if you are extracting a fume or a vapour and the difference in controlling them.

See our welding extractors, solder fume extractors, laser fume extractors, solvent extractors and fume cabinets for more information on available products.