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 during transit.
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.
Negative Pressure Unit (NPUs)
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