RETA Breeze Jul-Aug 2025

Two examples of refrgerated makeup air units.

facility. This makes sense when you think the air should flow opposite to the product. The difference in pressures helps establish that air flow pattern. However, there is a fine balance with this, as there is such a thing as too much or too little airflow. To further put this in perspective, these pressures are measured in inches of water column, which means extremely small changes can make a world of difference, good or bad. When designing plant ventilation, there are three basic concerns to take into consider ation: 1. Temperature of the individual areas of the plant: this reduces the chances of product spoilage. Consider that in poultry, salmonella begins to bloom at ±43°F. Sanitary considerations: making the building and equipment easy to clean reduces the chance of transferring bacteria. Moisture control: keeping the plant dry as much as possible. Bacteria thrive in wet environments, and some thrive in wet and colder environments. 2. 3. BASICS OF CONTROLLING BUILDING PRESSURE Process or production plants never maintain a constant air pressure due to opening and closing of the main doors, automatic rollup doors, exhaust fan cycling, etc. Some plants use a constant airflow via make up air and exhaust as a simple solution. However, in today’s world of needing to enhance food quality and food safety, automation comes into play.

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supply air;

o Evisceration:

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exhaust air; and

 This area of the plant comes after the feathers have been removed, internals removed and other processes take place. A complete air exchange every 2–3 minutes. Air entering Evisceration is typically filtered using 10-µ filters.  Area pressure is slightly positive. o The bird chiller area (for whole birds minus the head, feathers, feet and internals) is used to bring the bird temperature down from 98°F to 33°F–34°F internal temperature measured in the deep breast tissue.    The ideal air temperature is 70°F–75°F.

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dust collection.

Ideally, you would want air blowing (through nozzles, hoods, or diffusers) down on each employee working in this area in the range of approximately 1,000 to 1,200 CFM and 60°F–65°F air per employee. Dust collection is necessary for the capture of dirt, dust, feathers, etc. The hanging pen should be slightly negative compared to the pick/scald area in the magnitude of 10% or less. This is critical as the first step in keeping dirty air from entering other areas of the plant.

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Area pressure is slightly positive.

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o Some plants combine areas such as the Pick/Scald room which usually also houses the “blood tunnel.”The scald

o Debone:

In plants that have a debone department, it is typically the highest internal building pressure.

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process typically consists of using hot water (upwards of 130°F water) to loosen the skin for feather removal.

o Portioning:

 Offal and other support rooms such as shipping docks, blast cells, holding freezers, tub/tote wash, wastewater treatment, etc. Air will ideally flow from the cleanest part of the food or process area to the dirtiest, as a rule of thumb. In the case of poultry processing, the “debone” or “second processing” areas will typically have the highest air pressures in the plant, while areas like the “picking or scalding” will have the highest exhaust fan draw on the

In this area of the plant, due to this area constantly being hot and humid, control of condensation is critical. The ventilation rate is high with exchange rates in the range of 1–2 air changes every minute. This area has a slight negative air pressure condition.

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