How risk-based air monitoring supports zoning verification, trend analysis, and stronger EM programs.
In this article, you'll learn:
Air is an important but frequently underestimated route of contamination in food manufacturing. Airborne particles can carry bacteria, yeasts, molds, and spores into production environments — particularly where there's exposed product, elevated water activity, movement of people or materials, or poorly controlled airflow.
The Safe Quality Food (SQF) ambient air testing guidance explicitly recognizes air as a potential contamination vector, while the Codex Alimentarius General Principles of Food Hygiene (CXC 1-1969) require food to be produced in environments that minimize contaminants.
Scientific literature supports treating airborne contamination as a genuine food safety concern. A 2024 International Journal of Food Microbiology review concluded that airborne microorganisms in food-processing environments pose a meaningful contamination risk, while also noting that the industry lacks tailored quantitative guidelines and harmonized sampling approaches (Loveniers et al., 2024).
That absence of harmonization is precisely why a structured, risk-based environmental monitoring (EM) strategy matters for both regulatory confidence and practical process control.
Out-of-specification microbiological results are recognized as critical indicators of underlying process or hygiene failures, particularly at a critical control point (CCP). Such deviations cast doubt on the microbiological status of all products manufactured since the last verified state of control, often necessitating holds, intensified investigations, and corrective actions — with significant potential consequences for productivity, compliance costs, and consumer confidence.
Active and passive air monitoring answer different questions
The two principal microbiological approaches to air monitoring are passive and active sampling. Passive monitoring uses settle plates exposed to the environment for a defined period, allowing viable airborne particles to settle naturally onto the medium before incubation. Active monitoring uses a microbial air sampler to draw a defined volume of air onto a culture medium, after which colony-forming units (CFUs) are incubated, counted and, where necessary, identified.
These approaches answer different questions and are best used together. Passive monitoring is particularly useful for understanding how airborne contamination settles onto surfaces and exposed work zones over time. Active monitoring is more appropriate when the objective is volumetric, quantitative data that can be compared across locations, time points, and production states.
SQF guidance notes that active monitoring devices are better suited to environments where microbial concentrations are low, because viable contaminants are less likely to be missed than with passive monitoring alone.
What air monitoring reveals about contamination risk in food production
Published research from food production environments makes a consistent case for giving air monitoring a defined role within broader EM programs.
In a two-year study of a medium-sized dairy-ingredient plant in Ireland, Zacharski and co-workers analyzed 3,468 microbiological tests across 124 fixed sampling locations, including 1,787 air samples. Their passive air sampling analysis identified higher-risk areas within the plant, particularly bulk packaging, atomization, and fluidized-bed areas. It also demonstrated that combined air and surface data could be used to optimize sampling effort and corrective action planning (Zacharski et al., 2018, Journal of Food Protection).
In a study of airborne fungal contamination in a dry-cured meat production facility, Asefa et al. (2009) compared active air sampling with settle plates. They found that the active sampler recovered higher mean CFU per plate and more fungal species, while both methods identified similar dominant genera.
Dragoni-Rosado et al. (2023) analyzed airborne bacteria across two dairy farms using an SAS air sampling system. They identified 63 bacterial genera, and found meaningful differences in airborne bacterial burden between sites, with location, temperature, and relative humidity all cited as influencing factors.
A 2025 full-scale meat-processing study combined qPCR detection of airborne Shiga toxin-producing Escherichia coli (STEC) and Salmonella with computational fluid-dynamics modeling. Results indicated elevated pathogen concentrations in high-risk areas such as dehiding rooms, and demonstrated that air curtains reduced pathogen spread between zones.
Taken together, these studies reinforce a consistent operational message: airborne risk is site-specific, process-specific, and zone-specific. Monitoring is most valuable when it reflects actual contamination routes rather than a fixed sampling routine lacking spatial logic.
Hygienic zoning and microbiological monitoring expectations
European Hygienic Engineering and Design Group (EHEDG) guidance on hygienic air quality adopts a risk-based framework. Expectations rise as product exposure and sensitivity increase, moving from Basic Hygiene (Zone B), through Medium Hygiene (Zone M), to High Hygiene (Zone H).
In Zone B, microbiological air monitoring may be applied selectively where there’s a known process risk or historical concern. In Zone M, routine monitoring is recommended to verify that ventilation, filtration, and hygiene practices are performing as intended. In Zone H, air monitoring’s essential, providing ongoing confirmation that air quality remains under control where contamination consequences are most severe.
Within this framework, air monitoring plays a key role in confirming that zoning controls remain effective.
What the standards and regulations expect
In the European Union, the legal foundation is Regulation (EC) No 852/2004 on the hygiene of foodstuffs. This places food safety responsibility on the food business operator, and requires procedures based on hazard analysis and critical control points (HACCP) principles.
FSSC 22000 requires a risk-based environmental monitoring program with documented controls, trend analysis, and periodic review. SQF guidance explicitly requires ambient air testing in high-risk processing areas, and recognizes both active and passive monitoring approaches.
In the United States, the Food Safety Modernization Act (FSMA) Preventive Controls rule (21 CFR Part 117) requires manufacturers of ready-to-eat (RTE) foods to implement and verify preventive controls where environmental contamination is a reasonably foreseeable hazard.
FDA guidance recognizes environmental monitoring as an important verification tool in high-risk processing environments, particularly where products are exposed to the environment before packaging, and no later step that would kill microorganisms is applied. In that context, air monitoring helps confirm that cleaning practices are effective, and that hygienic zoning controls are working as intended as part of a science-based EM program.
Selecting samplers and media
The reliability of air monitoring data depends not only on the sampling approach, but also on the consistency of the sampling equipment and the suitability of the culture media used. Active air samplers are designed for volumetric microbiological monitoring, enabling reproducible data collection. This supports meaningful comparison across locations, time points, and production conditions.
Systems based on multi-point impaction principles, where air is drawn through a perforated sampling head onto a standard culture plate, are widely used in food manufacturing because they provide defined, measurable air volumes, and consistent recovery of microorganisms. This makes them well-suited to applications such as zoning verification and microbiological trend analysis. SAS air samplers are an example of this type of impaction-based system, and are commonly used for routine environmental monitoring in food production environments.
The selection of culture media should be based on the expected microbiological flora and intended purpose of monitoring. Guidance such as ISO 14698‑1 recommends the use of non-selective media as a default for general EM purposes. Where necessary, additives should be included to neutralise disinfectant residues and support recovery of stressed organisms.
In practice, general-purpose media such as Tryptic Soy Agar (TSA or SCDM) are used for total viable count (TVC) monitoring, typically incubated at 30–35 °C for at least 48 hours to recover mesophilic bacteria. In parallel, fungal media such as Sabouraud Dextrose Agar, Rose Bengal Agar, or Potato Dextrose Agar (PDA), often containing bacterial inhibitors, are used to enumerate yeasts and moulds, with incubation at 20–25 °C for 5–7 days.
Where specific pathogens represent a defined risk, selective or chromogenic media may be used following appropriate validation. For example, COLOREX™ Listeria enables rapid presumptive identification of L. monocytogenes, although suspect colonies must be confirmed using recognised biochemical or molecular methods. For a fuller discussion of Listeria detection and environmental monitoring in food manufacturing, see our article on Listeria in Food Manufacturing.
Ready-to-use, quality-controlled media formats such as Redipor are often preferred in routine monitoring, as they help minimise preparation variability, and support consistent recovery across repeated sampling points, ensuring results are scientifically robust.
Where continuous disinfection fits into contamination prevention
Air monitoring provides insight into contamination risk, but does not in itself reduce microbial load. Interest is therefore increasing in technologies that support hygiene control continuously between routine cleaning procedures, particularly in high‑risk food production environments.
Peer‑reviewed research indicates that antimicrobial blue light at 405 nm can reduce the viability of microorganisms in surface‑associated contamination models and biofilms under controlled conditions. A 2019 Frontiers in Microbiology study by Ferrer-Espada et al. reported reductions in viable counts within polymicrobial biofilms following exposure to antimicrobial blue light, with effects confirmed using both culture-based methods and microscopy.
A 2025 Microbiology Spectrum study by Hur and Diez-Gonzalez demonstrated that susceptibility to 405 nm blue light varied substantially between organisms and test conditions, highlighting the importance of dose, surface type, and microbial composition in determining outcome.
These findings reinforce an important principle for food manufacturers: supporting hygiene technologies can contribute to contamination control, but their effectiveness is highly context‑dependent, and must be understood within the wider environmental and process conditions of the site.
Spectral Blue MWHI® applies this scientific and patented principle through a multi-wavelength, high-intensity visible blue light system designed to provide continuous, automated operation. Intended to complement established cleaning and disinfection programs, it reduces background microbial pressure between routine cleaning events, rather than replacing conventional hygiene controls. As with any supporting technology, site‑specific validation and risk assessment are essential to confirm suitability and performance within a given production environment.
Making air monitoring work
The scientific evidence is clear: airborne microbial risk in food production is real, site-specific, and process-dependent. A risk-based air monitoring strategy — applying passive and active methods appropriately, selecting culture media suited to the target organisms, and integrating monitoring data into trend analysis and corrective action workflows — adds genuine value to EM programs, and supports regulatory compliance.
Trend data is as important as individual results: a pattern of low-level positivity in a defined area is a more actionable signal than an isolated detection, because it points to a persistent source rather than transient contamination.
Air monitoring identifies risk; addressing it requires a layered approach. If you're building or reviewing your facility's EM program, AnalytiChem can help — whether that's selecting the right sampler and media for your production environment, or integrating continuous disinfection into an existing hygiene strategy. To discuss your specific requirements or explore how these tools work together, contact our team.
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