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CARPET & RESTORATION
Containment: The weapon of
choice in mould remediation
By Brad Prezant*
As a “mould warrior” or more commonly
known in the correct circles, a mould
remediator, you are constantly fighting a
war. Whether daily, weekly or monthly,
you battle against a very small, incredibly
durable, micro-sized enemy, invisible to the
This enemy has the ability to survive a
wide range of temperatures, can withstand
harsh chemical attacks, cannot be drowned and has an uncanny
ability to camouflage itself among the most ordinary dust.
We’re talking about fungal particulate – whole intact spores
capable of germinating, broken spore fragments, and pieces of the
bodies of living and desiccated moulds which, when inhaled by
unsuspecting human hosts, can have drastic health effects.
Before your own battle begins, you have to understand that you
must strategically approach the enemy by devising systems to
discover, collect and contain it which will work despite your inability
to visualise its presence.
Erecting containment, generating and directing the air flow within
that containment will enable us to win the air war, by controlling the
Where is the most strategic location of this containment? It should
be placed as close to the source of invasion as possible while still
permitting us to gain access and accomplish our work.
One of the most common flaws in mould remediation projects
is a containment structure that is larger than it needs to be; larger
containments require more equipment for managing airflow, have more
possible leak points, and require more time and effort to decontaminate
prior to de-mobilisation. While erecting a containment, one must
carefully balance the trade-offs between size and work access.
To do so, one can rely on the knowledge of experienced mould
warriors and follow the established principles.
Principle 1. Choose the smallest possible
surface area with the fewest ‘seams’
A curtain is the structure for our containment but a curtain does
not cause air to flow. Fans cause air to flow. If we are to control
the air war, we need to control the airflow. For true functionality,
we need fans capable of creating a pressure differential of sufficient
magnitude that it can overcome any other air currents, but not too
strong that it creates eddy currents in the opposite direction (watch
the area upstream of a large rock in a swift-flowing river and see
the direction of flow of fallen leaves. Air is just thin water, both are
fluids, and both behave identically). To control the air war, control
the airflow by sealing the edges of the containment.
Principle 2. Effectively seal the
edges of your containment.
The amount of suck we apply to our containment is determined by
the amount of leakage, regardless of the size of the internal area of
the containment. Build a containment with minimal leakage, and a
specified pressure differential can be maintained with a small fan.
Build one with lots of leakage and it will require a lot more suck to
Sealing the edges will ensure that the leakage into the containment
comes mostly through the intended pathways – the traffic area for
personnel and equipment, and the waste removal area. We will need
inward airflow in these transit areas to prevent dust containing our
enemy to escape by hitching a free ride alongside people and equipment.
Build a containment where most of the volume of air exhausted
by the fans is used to overcome diffuse leakage from poorly sealed
edges and the directional airflow will not be easily achieved and
maintained where it is most needed.
Principle 3. Always measure the pressure
differential of containment to ensure
adequate airflow management
Fortunately, we have a way of measuring whether the fan size is
properly matched to the effective open area of the containment by
measuring pressure differential. An electronic or mechanical dial-
type instrument known as a manometer or micromanometer, with
one tube attached to the interior of the containment and one tube
attached to the exterior of the containment will show precisely how
good a job you’ve done in sealing those edges.
Whether you express this differential in pascals (metric) or inches
of water column (an obsolete system surprisingly still used by
otherwise intelligent people) it should match your company’s SOPs
or the job specification’s recommended pressure differentials for
The correct differential will provide sufficient flow for controlling
our enemy’s movements without creating eddy currents allowing
them to sneak through our defences.
Build a good containment with sealed edges and monitor the pressure
differential and you effectively have both structure AND functionality.
Principle 4. Ensure make-up air entering
the containment is free of fungal
particulate and general particulate by
minimising the volume of air and HEPA
filtering it prior to entry
There is another reason to properly seal the edges. Since our
enemy is camouflaged within ordinary dust, all leakage points are
sources for the entry of external dust. There are two ways this
can lead to problems.
One is if that dust is hiding our enemy – the classic Trojan horse
invasion. If there is a source of fungal particulate outside the
containment, it can be brought in with the containment make-up air.
Our efforts to remove the fungal particulate within the
containment will then be compromised by an ongoing source of new
fungal particulate from outside the containment, and no matter how
much cleaning we do it will be replaced with new fungal particulate.
Not a situation leading to victory in the war.
Secondly, if the areas outside the containment are dusty, or
contaminated with construction or demolition debris absent fungal
particulate, we will have a very difficult time achieving clean
interior surfaces within the containment and will likely fail a visual
inspection, despite the absence of fungal particulate.
Brad Prezant is the chief scientific officer of ValidAir Sciences
This article first appeared in the February 2017 issue of R&R
Magazine and has been republished with permission.
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