Air filtration for laboratory environments

Camfil Australia Pty Ltd

Wednesday, 01 April, 2020

Air filtration for laboratory environments

There are many aspects to consider when maintaining effective air quality and freedom from contamination in pharmaceutical, biotech and hospital laboratory environments. Obvious considerations include compliance (or better) with various state and federal standards for air changes, room pressurisation and filtration levels.

Most air filtration systems focus on providing particulate free air; however, it is worth considering that there are molecular, non-particulate contaminants that will not be controlled via conventional filtration technology.

If we look broadly at air quality within a facility, internal air quality is equally as important as the quality of air being exhausted from the building. Both are considerable aspects in worker safety and the wellbeing of workers in and around the facility.

Most readers will be very familiar with HEPA filtration units of various configurations within the facility. Generally large units are wall or roof mounted to give the appropriate ‘face area’ that is appropriate to the required air flow for the room.

Unit size is typically driven by two considerations: the required air flow and filter testing access. A comparatively large surface area is required to achieve an appropriately modest air flow rate through the filter (for effective filtration and reasonable static pressure drops). An incorporated filter access panel is convenient for NATA certification or HEPA integrity testing to assure air quality on a yearly basis.

Less visible to the users of the facility are the array of critical items that support these HEPA filtration units. These items include clean ductwork, effective and reliable fan and thermal control units, insect prevention inlet grills and pre-filters to remove larger particulates. In some cases UV germicidal systems to limit pathogen loads are also utilised. All of these items must work in a coordinated manner to assure cost-effective and reliable delivery of air that is particulate free to acceptable levels.

In a variety of isolation and containment situations specified by AS/NZS 2243.3, BIBO (Bag In/Bag Out) airborne containment systems will be required.

Molecular contaminants have significant impacts on the health and wellbeing of the staff and clients in these facilities. Generally unnoticed, unless associated with offensive odours, these contaminants form a very important aspect of the air quality within a facility.

Molecular contaminants can commonly include acidic gases, bases, condensables (that can condense on clean, cool surfaces), organometallics, and sulfur and nitrogen oxides. Ozone can be an issue in some circumstances as well.

These items can be sourced from outdoor entrainment, scientific or medical devices, fugitive emissions from process equipment, chemical storage areas or laboratories, and temporary emissions from construction or repairs.

Significant loads of undesirable chemicals can also be introduced into buildings from heavily used car parks, emergency delivery docks or helipads, which in turn affect the ‘clean air’ systems of these facilities. The reader will be familiar with the types of airborne chemicals of concern in this area — carbon monoxide and dioxide, sulfur and nitrogen dioxide, reduced sulfur compounds, halogen gases, ozone, and chemicals associated with fine diesel particulates. In more rural areas, materials associated with fertilisers and insect control measures may also feature on the list.

Indoor contaminants are seldom considered, but can be especially relevant in new or recently renovated buildings. The off gassing of building materials and furniture, human activities, cleaning chemicals and test and maintenance materials can introduce significant chemical load to the interior of the building.

By way of example, we can consider the impact of airborne chemical contamination on IVF clinical environments. Success rates have been linked to aspects of chemical air quality in the clinical environment.

A variety of chemicals from outside sources may impact on these IVF environments, including automotive and diesel contaminants from helicopter pads and outside areas that can be included in makeup air, as mentioned previously. A control strategy for these items includes both conventional particulate removal and chemical absorption by dry media materials housed in filters or scrubbing units.

In general terms, chemically contaminated air is passed through beds of dry media particles at a predetermined rate and residence time. Designed and implemented correctly, these filter beds are able to remove more than 99% of many common contaminants.

The process of chemisorption, absorption and reaction that are employed are complex but well understood. Materials are readily available and consistent in terms of quality and performance. The media have extremely high surfaces area, similar to activated carbon; however, base materials like activated alumina and impregnates like permanganate may be used to provide superior retention and binding capacity of contaminants.

The consumption of the dry filter media is directly driven by the contamination load — the more contamination, the more material that will be used. Generally an aim of the system design will be to give one year of life between change-out of filter media. However, real-life application can only be determined in practice. Sampling of the media is possible for exhaustion testing — so that the remaining media life can be calculated. The media essentially works at 100% of the nominal efficiency until exhaustion, then this efficiency plummets to zero.

In most cases, the media is general waste, which makes it relatively easy and inexpensive to dispose of. When used in radio-nucleotide or particularly hazardous environments, testing before disposal will need to be done.

The range of uses in clinical environments for this chemical scrubbing material is extensive. Examples include odour control for insulin production, ammonia scrubbing for research animal enclosures and removal of fugitive emissions for sterilisation units. There are literally solutions for any chemical material that can be safely absorbed and recirculated.

There are several layers of air filtration and purification that can be used together to assure high-quality air in hospital, clinical and pharmaceutical/ biotech environments.

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Image credit: © photo

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