ductless ventilation in
fume cupboards
Technical Sales Manager Geoff Edwards, briefly discusses the importance of
industrial fans in ductless recirculating fume extraction systems.
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.
D UCTLESS E XTRACTION : H OW D OES
T HE P ROCESS W ORK ?
1. Hazardous particles, vapour or fumes
are pulled into the filtration system
by the unit’s powerful fan.
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
B ENEFITS OF S ELF C ONTAINED H OODS
The principle is simple, air is drawn in
through the front opening of the fume
cabinet, circulated through a filter, and
then expelled back into the lab via a
fan. Ducted systems are a necessity
and preferred in many instances, such
as chemical and hazardous fume
applications, but there are many
considerable advantages to using new
ductless fume hoods:
E NVIRONMENTALLY F RIENDLY
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.
E NERGY E FFICIENCY
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.
M INIMAL M AINTENANCE
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.
I NDUSTRIAL F ANS FOR D UCTLESS F UME
E XTRACTION S YSTEMS
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.
EC B ACKWARD C URVED C ENTRIFUGAL
F ANS
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 e-wheel are also available
on request. For more information visit our
Backward Curved Centrifugal Fans page.
EC F ORWARD C URVED C ENTRIFUGAL
F ANS
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.
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 our website, our
corrosion resistant fans are also available
in ATEX certified units.
www.axair-fans.co.uk
Issue 29 PECM
17