Case study: How to optimize air quality in an industrial food packaging facility

Production insights

• High-efficiency particulate air (HEPA) filters are used in the HVAC system to ensure a high level of air filtration
• Fine powder products are sensitive to humidity in the air, creating specific challenges when designing air flow.

Many of the design features in industrial facilities are comparable to commercial design considerations. However, one of the major differences is in the level of precision that has to be applied to most of the design parameters in industrial facilities.

An example is a design for a major nutraceutical brand that was expanding the production capacity for their main product line. The product is a granulated powder nutritional supplement that is very sensitive to humidity. Additionally, being a fine, powdered product, the design had to consider that the product can easily become airborne from heating, ventilation and air conditioning (HVAC) system drafts, especially in the flavor additive (kitting) process and in the blending of the flavorings and product base. Additionally, the product kitting, blending and filling processes do not have a heat-treating step that would provide a means to neutralize any airborne introduced pathogens that may be introduced from lower hygiene spaces or the ventilation air stream.  Additionally, a Dust Hazard Analysis was performed per NFPA 652 – Standard on the Fundamentals of Combustible Dust, to ensure the product did not pose a combustible dust hazard.

The HVAC design had multiple layers of filtration of the conditioned air entering the production space to ensure the air being introduced was as free of impurities and potential pathogens as reasonably possible. At the same time, the system filtered the dust-laden return air before it could combine from various other spaces into a common duct that returned recirculated air as part of a cross-contamination control strategy.

Other than the significant level of filtration with HEPA filters on the supply and return air ductwork, the system flow diagram looks like a fairly conventional variable air volume HVAC system. Additionally, the rooms are pressurized to create a high-pressure, high-care hygienic zone wherever there is open product and to pushes that air out to lower-care adjacent spaces. If space had permitted, there would have been additional transition zones between the production spaces and the warehouse, similar to the clean corridor on the back side of the production rooms. In lieu of the transition zones, there is a higher amount of pressurized transfer air continuously pushing air out to the warehouse, even when the production equipment stops — ensuring a continuous high-care environment for the open product handling and filling areas.

Figure 1 is simplified from the true production line, but contains all the design features and types of rooms that the project air handling system ultimately contained. The project is designed and currently beginning construction.

Figure 1: This airflow and pressurization diagram shows the pressurization acheived through air balance differentials. In critical applications, the high hygiene spaces may have data-logged pressure monitoring to establish that the design conditions have been maintained during active process operations. In this particular application, the production spaces will have LED pilot lights indicating the space is pressurized to a target setting, making it suitable for production activites. Courtesy: BW Design

General air quality considerations

This case study demonstrates that the design of Indoor Air Quality and Indoor Environmental Quality (IAQ/IEQ) features in industrial facilities have most, if not all, of the concerns and criteria of commercial buildings, along with additional design considerations with greater focus on hygienic zoning and contamination control. The impact of IAQ/IEQ in industrial facilities affects not only the occupants, but also the large quantities of mass-produced products and their consumers.

The design features in industrial facilities are generally similar to those in commercial facilities in terms of building construction and certain aspects of the major systems for air conditioning, fresh air ventilation and contaminated air exhaust. Where they deviate is in the primary focus of conditioning the environment of a process versus the conditioning the building occupants’ environment. Additionally, the level of precision in the controls for industrial processes can be far higher due to lower tolerance for deviation from established, specified setpoints needed to ensure a consistent, repeatable process.

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