How to Choose the Right Filters for Your Fume Hood

Ductless fume hoods or fume cupboards are often used in laboratories to capture and remove hazardous substances from the air which are produced during certain laboratory applications. These can be gases, vapours, aerosols or particulates (dust). The fume hood encloses a work bench area that has a fan unit at the top. This sucks the air from the front opening upward through filters which trap the hazardous substances. Clean air is then expelled back into the laboratory space. Ductless fume foods are seen as an easy to install alternative to more traditional ducted hoods, requiring little existing infrastructure and not requiring duct work. For more information, read our guide on the benefits of a ductless fume hood. [caption id="attachment_18515" align="aligncenter" width="300" class="center"] Erlab fume hoods accepts a number of filters, the most appropriate depends upon your chemical handlings.[/caption]

Chemical Filters

There are a few types of filters that could be required in a fume hood. Selecting the correct type of filters for your application is imperative to protecting yourself and your colleagues from any hazardous substances in the air. The most appropriate type of filter is dependent on what types of chemicals you will be using in your daily handlings. Activated carbon filters are created by steam heating charcoal and graphite at high temperatures (up to 980°C). This separates the layers of crystalline carbon and creates a large internal volume which allows for adsorption of chemical particles to occur. The activated carbon is then impregnated by pre-adsorption of a chemical that will react with the pollutant that the filter is intended to trap. Four different types of activated carbon filters are commonly provided. These are filters that can trap organic, ammonia, formaldehyde and acid vapours.

Particulate Filters

Hazardous particulates are filtered and trapped in different types of filters than chemical vapours. Usually this would involve a HEPA (high efficiency particulate absorbing) or ULPA (ultra low particulate air) filter. Both filters use layers of dense fibres to create a fine mesh filter that removes contaminants as air is forced through them. HEPA filters have a 99.97% filtration efficiency for particles down to 0.3 μm. The ULPA filters have a 99.97% filtration efficiency for particles down to 0.12 μm. So choosing between the two particulate filters comes down to the size of the particles you will be producing. Our Erlab fume hoods are capable of using both activated carbon and particulate filters to provide the top level of protection from your samples for most applications. But it is incredibly important to select the right filters for your application. This ensures all the hazardous vapours and particles are being captured by the filters and not being recycled back into your lab’s air supply.

Complete A Risk Assessment For Filter Selection

In order to ensure the correct filters are provided, our premier fume hood supplier, Erlab, have developed a quick and easy web tool called an eValiquest to run a risk assessment. This allows for a customized filter suggestion suited to your specific application. The results will also provide the recommended life time and quantity of the filters. Ductless fume hood filters need to be regularly changed (usually on a schedule between 6-24 month) in order to prevent over saturation of the filters. If the filters are not changed according to the recommended schedule, they can become oversaturated. This minimizes the ability of the filter to trap any more hazardous particles and renders the fume hood useless. If you would like to know more about our range of fume hoods or replacement filters, please contact us on sales@camlab.co.uk or visit our website.