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Ask an EHEDG Expert

EHEDG Connects poses simple questions to EHEDG Subject Matter Experts, and invites them to provide us with straight answers. Our questions on air handling are answered by Dr. Thomas Caesar, Director Global Filter Engineering at Freudenberg Filtration Technologies. Dr. Caesar is also the chair of the EHEDG Working Group Air Handling that developed EHEDG Guideline Document 47 on air handling systems in the food industry.

EHEDG Document 47 only focuses on air quality control for building ventilation. Why?
Dr.Thomas Caesar: “When our working group started to work on this guideline back in 2006, it didn’t take us long to understand that in order to enhance the practical value of the  guideline, we first needed to narrow down the scope of the contents. After all, what use is a guideline that tries to cover everything, but only scratches the surface of the various food safety determining types of air handling? EHEDG Guideline Doc. 47 is a comprehensive document, that is closely aligned with EHEDG Guideline 48 on building design (as it should be), and it now offers a valuable insight in air quality control for building ventilation.


Of course, our working group also plans to publish a guideline on air handling for process oriented air handling as well, but since it’s all purely voluntary work, it will take us more time to complete it.”

What’s so complex about air handling that we need multiple guidelines for it?
“For starters: air is everywhere. In almost all food processes, even closed ones, food gets into contact with the air surrounding it. If this air contains particles that microbes can attach to, food safety risks may arise, so a well thought-out approach to air handling is fundamental for food safety. Since air tends to move around through freely through production plants, we need to approach air handling on all levels - from building ventilation to exhaust air, dust handling and compressed and non-compressed air flows. Each level is a world on its own and should be covered by a dedicated EHEDG Guideline Document. Our working group started off with narrowing the guideline down to building ventilation as this is applicable to many different types of food processing. Our next guideline, however, will focus on process air filtration.”

How do I know if my air handling is effective? 
“You can install particle counters that provide a better insight in the contamination risks connected to air quality. Since micro-organisms can only spread through the air if the air contains particles that the microbes can attach to, it is safe to say that minimizing the number of particles in the air benefits food safety. Despite of the availability of new technical solutions to monitor air quality in food processing environments, there are still many food producers that only start to improve air handling systems after they are confronted with serious product quality fluctuations. This is mainly due to the fact that most monitoring systems are still quite expensive. The most cost-effective way to monitor the air quality is to monitor the amount of airborne particle in the active air handling units. To do this, you can add special membranes to the filter units that collect the particles and allow users so you can grow and count them. Before you do this, you need of course to know what your critical control parameters are for your specific product.”

Dr. Thomas Caesar [interview continues below picture]

What are the most common causes for food contaminations by air?  
“Air connects everything: exteriors and interiors, different building zones and everything within it. A common cause for bad air quality is bad air flow design. We often see plants with air flowing from a contaminated (technical) area to critical food processing areas. A general rule of thumb is to always lead the air flows away from the critical process areas. That can be quite a challenge in big open spaces with multiple food processing lines. If you don’t have a good understanding of the actual air flows in your building, it can be difficult to pinpoint air quality issues related to the zoning design. Examining the sources of the airflows is also a good way to start your investigation. Since most buildings make use of recirculated air, major causes of air contamination can often be traced back to dirty or wrongly installed pocket air filters in the air handling systems, or bad water quality in the humidifier. Installing a filter unit directly above a wet floor doesn’t help either. We recommend to use exclusively EHEDG certified air handling components, but it’s not only the design of the air handling system that counts, it’s also how the people use it, how the maintenance is performed and so on. It’s all connected and each air handling system is as good as its weakest link, so you need a comprehensive approach to really optimize food safety in a sustainable way.”

What would be the best steps to take in order to improve air handling?
“It all starts with describing your critical control parameters, with making a thorough risk analysis and with qualifying the specific needs for your type of food product. After that, you can consult the EHEDG Guideline Documents. Zoning generally has a big impact on air flows, so the EHEDG Guideline on Building Design is a good document to start with. Then continue with our guideline on air handling with regard to building ventilation. These two guidelines are strongly intertwined, so we made sure that they are well aligned with each other. A relatively new and effective trend is to install air handling units directly at the points where the most critical process steps take place. This enables food producers to decouple their most critical processes from the rest of the air flows in a production environment. Since these locally focussed systems generally need to move much smaller volumes of air, they need less ventilation power than conventional systems and therefore can provide additional benefits like a significant reduction of energy consumption. In the end, it’s all about minimizing risks on all levels, from the engineering and design up to the daily usage and maintenance of the air handling systems.”

EHEDG members can download EHEDG Guideline Doc. 47 for free here: