Extraction technology in powder, food, and pharmaceutical production

Every transfer point in the packaging line is a potential entry point for dust and contamination. In food and pharmaceutical production, the cleanability of the extraction technology determines the approvalability of the system. ULMATEC Filtration demonstrates at Powtech (September 29 to October 1, 2026, Nuremberg, Hall 7, Stand 7-838) how this can be implemented. (Copyright: parilov evgenii / Parilov@AdobeStock (No AI marking))

In many facilities, the exhaust system has been running in the background for years. It is not included in any recipe approval, even though it is the only component that touches each batch. Why the filter becomes the biggest risk, and what needs to be done differently in its design.

A plant changes the filter cartridges on a Friday afternoon. Two people, supervisor, half an hour of work. What gets into the air depends on the design. Comparative measurements on airborne particle filter systems showed 0.49 µg/m³ residual dust with a safe-change system and filter wetting, without both, 105 µg/m³. A factor of 200 difference with identical effort.

The EU-GMP Annex 1 guideline has required since 2022 a contamination control strategy throughout the process. A filter cassette that releases active pharmaceutical ingredient dust during change belongs there.

A filter housing that no one can access is not cleaned

Regulation (EC) No. 852/2004 in Annex II Chapter I Number 5 requires avoiding artificially generated air flows from a contaminated to a clean area. The same paragraph states that filters must be easily accessible.

Applying this to an existing system, findings are almost always present. A duct over a zone boundary. A housing that can only be opened with tools. A horizontal stretch without slope. Standards exist for the geometry: DIN EN 1672-2 prohibits dead spaces and gaps, EHEDG Document 8 recommends a Ra value of 0.8 µm or better, internal radii of at least 3 mm, and a minimum of 3 degrees of inclination.

Dust in the filter ignites more easily than in the silo

An exhaust system not only separates dust from air, it sorts by grain size. What reaches the filter is the fine fraction, which is more explosion-prone. For grain dust with a median of 160 µm, the Research Society for Applied System Safety reports a KSt value of 89 bar·m/s. For the mixed dust from the filter, under 37 µm, it is 131 bar·m/s. The minimum ignition energy is usually below 10 mJ.

Therefore, TRGS 722 classifies the interior of system parts and pipelines as Zone 20. Of 70 documented fires in dust extraction systems, 80 percent occurred in bag filter systems according to insurance data, with 48 percent of ignition sources being static sparks.

As soon as POM enters the machine, the formaldehyde level rises

Thermoplastics are processed between 170 and 310 degrees Celsius according to DGUV Information 213-728. Formaldehyde is released from POM, styrene from polystyrene, and hydrogen fluoride from PTFE. Without POM, concentrations at the workplace were mostly below detection limits. In POM injection molding, the 95th percentile for formaldehyde reached 0.235 mg/m³, nearly two-thirds of the limit value of 0.37 mg/m³, with two cases exceeding it.

From a filter technology perspective, the difficulty lies elsewhere. In a documented case at an extrusion plant, aerosols clogged the filter pores and hardened during cooling. The exhaust line had to be heated.

The suction power drops steeply with distance from the exhaust opening

According to DGUV Information 209-200, the intake velocity drops to 7.5 percent of the value at the opening itself one duct diameter upstream of the opening. If the hood is mounted further away because it otherwise obstructs, the system's effectiveness is halved.

“A volumetric flow alone does not determine how an exhaust system should be designed. Crucial is how many extraction points are actually operating simultaneously in practice. This number is surprisingly often underestimated during planning – with consequences for the entire system and the investment.”
— Maximilian Schuster, Sales Manager, ULMATEC Filtration

ULMATEC Filtration therefore designs according to calculation in lot size 1. For food and pharmaceutical applications in stainless steel, with planned cleanability. The calculation includes the simultaneity factor (GZF), the question of how many extraction points actually run together in practice. It is not specified in any standard and determines the size of the fan, connection power, and investment security.

Conclusion

Regulatory frameworks treat the exhaust system as a product-controlling component with its own explosion risk. When renewing or expanding a system, one should start with the process, not the equipment.