Failures in conventional air scrubbing and cleaning
Air filtration and cleaning has been undertaken for many
years but all methods have proven failures which are explained here.
This method generally relies upon physical capture mechanisms. Filters are
reliant in the laminar movement of air and the contamination it carries to pass through the filter.
This means the contaminated air must be ducted to the face of filters and that all air travels at the same velocity which must take into account the weight, size and aerodynamics of the particle to be captured. This is clearly impossible even in ducting as we see build up of contamination on surfaces even in high pressure ducting.
A view inside most ventilation ducting or ventilation systems proves filter and laminar air flow failure points as bends and corners can be seen to be filthy from drop out.
Please see description of why particles remain airborne for months and even years
The best type of filter available is classified as HEPA
but even these have major problems in
practice. They cannot trap odours or VOCs and most importantly must rely on
filter housing to be leak free. A major study has shown that most portable
devices leak through damaged or poorly fitting filter housing often caused
These systems provide conditioned air through a supply
system and air is returned by extract systems to a Air Handling Unit (AHU) These systems usually have very poor
filtration which can be seen by the build up of debris on ductwork internal
surfaces but more importantly almost all supply air is re-circulated extract
air with usually less than 10% being fresh air(to conserve heat)This means the
polluted air extracted from one room is re supplied to other areas in the
building. A check on the debris and mould formed on cooling coils and drip pan
of the AHU downstream of filtration shows how inefficient even commercial
systems are in cleaning air.
These units are used extensively in the asbestos removal
industry to reduce airborne contamination during the removal operation. It
should be recognised that the NPUs are mainly used to create negative pressure
within the work area to prevent any airborne fibres escaping into other areas.
The asbestos removal industry recognises the shortfalls of NPUs and apart from the need of workers to
wear powered respirators they must inject or cover substrates to be
removed with containment solutions to reduce airborne fibre release. NPUs suffer typical issues of filter
leak and must be tested regularly and also best practice requires a NPU with
roving head to be installed at the point of possible asbestos fibre release.
Typically the air just a few feet away from the NPU will be
not be clean as the unit cannot pull air from any distance by suction alone.
In this process a chemical is fogged into the air to mask
odour or sometimes kill bacteria and mould.
Odours especially bad ones are natures warning that
something is possibly hazardous and masking with another chemical is extremely
bad practice and a possible increased hazard from introduced chemical masking
agents. The most significant issue of killing mould and bacteria is that the
residue becomes smaller and this residue contains or is covered in the same toxins
or allergens as when alive. These smaller particulates, often less than 5
micron can be readily inhaled but of particular importance is the access to
alveoli or lower respiratory system where blood oxygen transfer occurs. This
means dead or non viable mould spores and bacteria can be an increased health
hazard especially from fogging and application of any biocide.
A disinfectant may have 2% active ingredient or antimicrobial. It may have 1% surfactant with 97% water when
initially fogged. Since water evaporates
faster, the fogged droplets may float in the air with very little water with
greater than 50% combined antimicrobial and surfactants. The water will leave the air and attach to
dry surfaces. This is not how these
disinfectant formulations were tested for inhalation toxicology testing
required by government agencies. This is why breathing complaints occur
regularly from untrained individuals fogging formulations that were not
properly understood for this process.)
While opening windows may appear to reduce odour or humidity
the reality is that air leaving or entering a room will depend on laws of
physics and revolve around pressure differentials, laminar and turbulent air
flow. In basic terms even if a square room had a window open on all four walls
and gale force winds were present dead spaces would still be present in corners
etc. Practically speaking, opening windows and even fans will do next to nothing
in terms of decontamination and a simple smoke pencil test will prove these shortfalls
High Efficiency Particulate Arrest 99.97 of particles down to .3 of a micron