Do you know how cleanliness zones in food production are divided and how the degree of air cleanliness is determined?
2026-04-01
Food plant employees are often asked questions such as: Which areas of your facility are clean and which are semi-clean? How is this distinction made? What is the level of cleanliness in the clean areas? What are the microbiological control indicators? I believe that many of you will not be able to give an informed answer to these questions. However, without understanding these issues, we are deprived of the basis for planning the workshop and organizing sanitary control, and therefore cannot guarantee that sanitary conditions meet food safety requirements. Therefore, our editor, passionate about the topic of microbiological food control, spent some time systematizing knowledge in this area and sharing it with you, who love to learn:
How are sanitary classes determined in food processing plants?
To facilitate the design and sanitary control of various production areas, food processing plants (areas) are usually divided into different sanitary classes. According to GB14881-2013 General Hygiene Standards for Food Processing, they are generally divided into clean work areas, semi-clean work areas and general work areas. Semi-clean and clean areas are also grouped together under the general name "controlled production areas". According to the ISO 14698-1 standard “Biological cleanrooms - Control of biological contamination”, zones are divided according to the degree of biological contamination into low risk zones (negligible risk), medium risk zones, high risk zones and maximum risk zones. Foreign enterprises usually divide workshops into high, medium and low risk zones.
Let's let our domestic enterprises be guided by the GB14881 standard. The question arises: which areas/zones are classified as clean zones and which ones are quasi-clean? How exactly is this determined? In theory, the sanitary level of an area should be determined based on the risk of biological contamination of food products, as well as the presence of subsequent sterilization processes. Some domestic “Sanitary standards for food production” (the so-called GMP standards for the food industry) and the “Requirements for food processing establishments” standards issued by the CCAA have separate provisions with clear zoning criteria, for example, in paragraph 5.1.4.2 of the CCAA0016-2014 standard “Food Safety Management System - Requirements for Beverage Manufacturing Establishments”:
However, most GMP standards do not have clear zoning methods. What to do? In fact, we can use the zoning criteria set out in the GB50687-2011 Standard “Specifications for the construction of cleanrooms in the food industry”:
First category:classification criteria for common foods:
Second category:criteria for classification of dairy products
Third category:Beverage classification criteria
Of course, the above criteria are not absolute. Due to the individual nature of food processing, the degree of contamination generated during the production process, and the differences in cleanliness requirements of production facilities, a thorough risk assessment must be carried out and reasonable classification must be achieved.
How is the degree of air purity determined in a clean area?
We have determined the sanitary class of the workshop (zone), but a new question arises: how to determine the degree of cleanliness in a clean zone? First, let's look at the concept of “degree of purity.” According to GB50073-2013 Cleanroom Design Code (equivalent to ISO 14644 Cleanrooms and Associated Controlled Environments), the degree of cleanliness is defined as follows:
Degree of purity: the degree of purity determined by the number of particles of a certain size in a unit volume of air.
According to this definition, GB50073 divides the air cleanliness of clean areas into 9 classes (corresponding to ISO classes 1–ISO 9):
Astute readers may have noticed that here the degree of cleanliness is determined by the amount of suspended particles in the air, whereas in food processing plants we pay more attention to the state of microorganisms in the air (suspended and sedimented bacteria). Based on the above standard, it seems impossible to determine the cleanliness class of the food processing plant. In addition, we often hear the following class names: 100th class (class 100), 10,000th class (class 10,000), 100,000th class (class 100,000), 300,000th class (class 300,000). Why is this so? It turns out that according to the GB50457-2008 Standard for the Design of Cleanrooms in the Pharmaceutical Industry, the degree of cleanliness is classified as follows:
In addition, in Annex 1 “Sterile Medicines” to the new edition of the GMP standard for medicines “Quality Standards for the Manufacturing of Medicines (2010 Revision),” the degree of purity is divided into four levels: A, B, C and D:
Table 2. Standards for the content of suspended particles in the air of clean zones
Table 3. Dynamic standards for microbiological control of clean areas
In addition to the above classification standards, there are also US Federal Standard FDA 209E and standards from other countries, which we will not describe in detail here. At this point we are just familiar with the standards for classifying cleanliness levels, but exactly what level of cleanliness in the clean areas of our food processing facilities must be achieved to meet the requirements? Let's first check whether there are relevant provisions in the GMP standards for food products. In China, there are three main categories of food GMP standards: first, the general standard GB14881; secondly, sanitary standards for various types of food products; third, the manufacturing facility requirements issued by the CCAA to support the implementation of ISO 22000. Let's see if they have any provisions regarding cleanliness requirements.
This is not covered in the GB14881-2013 General Hygiene Standards for Food Production.
The CCAA 0010-2014 standard “Food Safety Management System. Requirements for enterprises producing seasonings and fermented products" this is also not specified.
In paragraph 5.1.4.4 of the CCAA 0016-2014 standard “Food safety management system. Requirements for Beverage Manufacturing Plants” mentions: “The ventilation and air purification system in clean areas of the plant must provide a degree of cleanliness that meets the requirements of applicable laws, regulations and standards.” However, it also does not specify which areas should achieve what degree of cleanliness.
In addition, the Food Microbiological Control Editorial Board analyzed 23 food industry GMP documents and 5 food plant inspection documents covering food industry sectors such as drinking water, beverages, dairy products, dry snacks, candy and chocolate, confectionery, bakery products, health products, baby food, egg products, etc., and summarized data on the control of microorganisms and dust particles in the air of the production environment. See Table 4 for details.
Table 4. Control of the number of microorganisms and dust particles in the air in food production conditions
From this we can conclude that, although our country has developed more than 20 categories of sanitary standards for food products (GMP standards), only a few of them contain specific requirements for the level of cleanliness of production facilities, and most do not have clear requirements.
Since many GMP standards do not specify cleanliness requirements for clean areas, what can be done? It is necessary to conduct a specific analysis for each industry, based on the characteristics of the food processing process, the degree of their exposure to contamination, and also taking into account the risk analysis according to the HACCP system. Or you can refer to the GB 50687-2011 standard “Technical conditions for the construction of clean rooms in the food industry”. This standard provides some guidelines for classification, I have cut out some of the text to show you. Personally, I think this standard is not strict enough.
Questions regarding inspection and confirmation of cleanliness
Another question we are often asked is: is cleanliness monitored in clean areas? Is this dynamic or static monitoring? Monitoring can be carried out in-house or entrusted to a third party; its purpose is to confirm compliance of purity with established requirements.
Internal monitoring is usually carried out once a week or once a month; Most plants are limited to monitoring settling microorganisms, while monitoring of suspended microorganisms and particles appears to be rare. This may be due to the limited capabilities of enterprises that do not have instruments to measure the amount of airborne bacteria and particles.
External monitoring is usually carried out once a year. In addition to the amount of deposited bacteria, airborne bacteria and particles, temperature, humidity, light, noise level, pressure drop, etc. are also checked, based on which a comprehensive assessment of compliance with standards is given. To determine whether the assessment is based on GB 50073 or GB 50687, the test report must be consulted.
Regarding static and dynamic monitoring, let's first understand these two concepts:
Static (At-rest) means: the facility has already been built, ventilation equipment and production equipment are installed, operating in a given mode, but there are no production personnel. Static monitoring is monitoring carried out in the absence of production after the start-up of ventilation equipment.
Dynamic (Operational) means: the site operates in accordance with established requirements, there are established personnel on the site, and work is carried out in an agreed manner. Dynamic monitoring is monitoring carried out under normal production conditions.
Many enterprises provide results of only static monitoring, but with dynamic monitoring, the indicators often do not meet the standards. However, the management of conditions in production areas must ensure that air quality meets standards even during normal production conditions, this is the only way to ensure food hygiene. Therefore, when designing production facilities, it is necessary to fully take into account dynamic environmental factors, such as patterns and volumes of material and technical movement, number of personnel, heat generation, dust, water vapor, pipelines, etc.
