Science laboratories within educational establishments such as universities and schools should be committed to ensuring that the users of ductless and ducted fume cupboards handling hazardous substances, are suitably protected from the inherent hazards associated with procedures undertaken as part of their duties. These units also have a duty to reduce both their carbon emissions and reduce overall energy consumption. This works alongside the Governments targets to reduce overall consumption and to improve energy efficiency initiatives. The large number of fume cupboards within universities, contribute significantly to both energy bills and CO2 output, and in order to lower this impact, energy saving principles must be applied to all new and existing fume cupboards.
Ductless fume hoods, Ductless containment hoods or self contained laboratory enclosures as they’re known are used within manufacturing, medical, chemical, laboratory and pharmaceutical and are negative pressure systems designed to protect the operator from hazardous fumes. The most significant difference between Ductless and conventional ducted systems is the exhaust method; in ducted systems the removed air is exhausted to the outdoors whereas ductless systems are designed to recirculate filtered air back into the immediate environment. The latter means that heated air is not expelled from the laboratory but also that noxious fumes are not expelled into the atmosphere.
1 – Hazardous particles, vapour or fumes are pulled into the filtration system by the units powerful fan. (more on this later)
2 – Air is processed through a pre-filter to capture some of the particles
3 – Air is purified by passing through a main filter. Options include HEPA, ASHRAE, Activated Carbon and speciality blended filtration media.
4 – Filtered air is distributed back into the immediate environment through a recirculating air pattern using no external ducting or venting
The principle is simple, air is drawn in through the front opening of the fume cabinet, circulated through a filter, then expelled back into the lab via a fan. Ducted system are a necessity and preferred in many instances but there are many considerable advantages to using new ductless fume hoods:
Ductless units recycle the air while cleaning the chemical mixture, so no fumes or hazardous particles are passed into the atmosphere, protecting the environment and exposed of correctly.
There is no potential to waste energy and increase costs that are associated with traditional ducted systems where heated or cooled air is expelled outside which then needs to be replaced by more air conditioned air.
Ductless systems are essentially a plug and play system with low set up costs and minimal installation. They can be moved easily to new locations as they require no venting. The only maintenance would be in removing, replacing and disposing of the saturated filter media and wiping down the unit regularly.
Recirculating fume cupboards are mainly used in educational purposes where the design of the building does not allow for fitting of external ducting, the fan can often be fitted underneath the worktop or above the workstation.
The fan and filter system is the integral part of the extraction hood, many also have built in air flow alarms or monitors which highlight when airflow is low or filter media is clogged. These procedures continue to ensure the safety of operators, students and staff. Speed controllers are also available which allow the user to set the centrifugal fan motor speed as desired to achieve the required airflow.
Centrifugal fans such as single or three phase direct drive units with ATEX certification are common due to the hazardous substances in question.
Our collection of EC impellers can be used effectively within re circulation hoods to deliver high air volume with low noise. These units take up less space than their forward curved counterparts and are available in a large range of sizes. Our collection of Ecofit RRE and modular versions of our EWheel are also available on request. For more information visit our Backward Curved Centrifugal Fans page.
Axair stock a wide range of EC forward curved centrifugal fans in single or double inlet configurations. Suitable for higher volume airflow, high pressure and larger recirculating cabinets with a low noise output.
For full information on our forward curved range visit our products page.
As we have mentioned, there are many fume extraction projects that require traditional ducted systems that would require corrosion resistant centrifugal fans that are situated at the end of the vented system to enable the fume to be expelled outside. For more information on this product range visit our polypropylene fans collection, also available in ATEX certified units.