ALARA Principles: Helping Keep Consumers and Producers Safe

Using the framework of ALARA to build a broader food safety philosophy

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10 Sep, 2026

Adam Green

The principle of ALARA, short for “As Low as Reasonably Achievable”, is a key part of both the creation and use of x-ray inspection systems in food production. X-ray inspection helps keep consumers safe from foreign objects such as metal, glass, plastic, stones, or bone. ALARA helps manufacturers develop policies, procedures, and risk assessments to use x-ray technology responsibly and safely. It can also be used to build a broader risk management philosophy: ALARM, or “As Low as Reasonably Manageable.” This article explores the key principles of ALARA and how it forms the foundation of ALARM.

Using x-ray inspection in manufacturing as part of a product safety strategy is very common. Many products used in daily life, including medicine, food, beverages, and even cosmetics, are inspected using x-ray technology. Over the years that x-ray inspection has been used, there have been no reports of adverse effects on consumers. Studies show that food can be exposed to far more radiation than it receives when passing through an x-ray system to inspect for foreign materials or other defects, and still remain safe for consumption.

X-ray inspection systems themselves are also safe to use, but only because of the effort that has gone into developing and designing safe ways to use the technology. X-ray radiation still has the potential to be dangerous, but modern systems are designed to keep the risk of exposure as low as reasonably achievable. The construction of x-ray systems used in manufacturing is governed by regulatory standards defined by governments - for example, 21 CFR 1020.40 in the United States, IRR 2017 in the UK, and GB18871-2002 in China.

ALARA and ALARP

ALARA is sometimes referred to by a different name, ALARP, or “As Low as Reasonably Practicable.” This term conveys the same idea as “As Low as Reasonably Achievable,” and the two are often used interchangeably. To avoid confusion, we use ALARA in this article.

X-ray inspection systems used in food production are known as cabinet x-ray systems. These systems use x-ray generators instead of naturally occurring radioactive material. As a result, the system does not produce radiation unless electricity is flowing through the generator. The use of a generator also allows for emergency shutoff mechanisms that cut power when the cabinet is opened, preventing x-ray exposure to operators. In addition, cabinet systems automatically shut down the x-ray generator in the event of any error or stoppage of the system. All METTLER TOLEDO x-ray systems are equipped with a warning light tower to indicate when the x-ray generator is active, along with warning labels in the local language to help prevent misuse.

METTLER TOLEDO takes several additional safety steps in the design of their x-ray systems. The generator is fully enclosed within the system cabinet to protect users from radiation exposure. In the past, lead was used as the primary shielding material in both the cabinet and the heavy curtains, but modern x-ray systems are generally lead-free and use other materials instead. The cabinet is locked to prevent easy access and is shielded with stainless steel, which absorbs x-ray radiation. Dense curtains are installed at the ingress and egress points of the conveyor to shield against radiation as products pass through the system. In the United States, the maximum allowable radiation leakage is 5 µSv/hour; in the rest of the world, it is 1 µSv/hour.

The unit used to measure radiation dose is the sievert (Sv). Because most everyday exposure levels are much lower, smaller units are commonly used: millisieverts (mSv), which equal one-thousandth of a sievert, and microsieverts (µSv), which equal one-millionth of a sievert. For context, the average person is exposed to about 2,400 µSv per year. Eating a banana every day adds approximately 36.5 µSv per year, frequent flyers receive an additional 200 µSv per year, and airline pilots and crew receive on average an additional 2,000 µSv per year. By comparison, the absolute maximum ambient radiation allowed from an x-ray inspection system is 1 µSv/hr, and most systems operate well below that level.

Symbol: rem
Full name: Roentgen equivalent man
Relation to SI unit: 1 rem = 0.01 sievert (Sv)

The rem is a non-SI unit used in the United States. It measures the biological effect of radiation by taking into account both the energy absorbed and the type of radiation. It is used in radiation protection, medicine, and safety regulations. The sievert (Sv) is the SI unit and is used internationally.

Radiation is emitted in waves, and, like waves on water, its intensity decreases as it moves away from the source. Put simply, the farther away you are from a radiation source, the safer you are. Placing obstacles in the path of radiation can also block or reduce the dose, so a combination of distance and shielding is most effective.

Time is equally important. Just as being farther from the source reduces exposure, spending less time near the radiation source also lowers risk. The best way to reduce radiation exposure is to avoid extended periods near the source of radiation. Spending less time in front of the system helps reduce the risk of exposure. This is one reason modern x-ray systems are designed to operate autonomously. Operators typically only need to approach the system during product changeovers or to clear an alarm, which further reduces exposure and helps keep operators safe.

Curtains placed at the entrance and exit of the x-ray system are designed to shield against x-ray radiation leakage. They should never be cut, tampered with, or removed from the system during operation, as this reduces or eliminates their effectiveness.

How Exposure Is Calculated

The dose rate for radiation exposure above normal background radiation is measured in µSv/hour. In other words, it describes the amount of radiation exposure over time at a given intensity. This value is then combined with the distance from the source to calculate actual exposure using the inverse square law. Under this law, exposure decreases in proportion to the square of the distance from the source. For a dose rate of 1 µSv/hour (or 0.0001 rem/hour), the exposure at a given distance can be expressed as 1/(distance)².

X-ray Inspection System Safety

System design and construction are one part of limiting the risk of radiation exposure, but another important factor is the policies in place for operating the system. This includes operator training in the safe and proper use of the system, as well as training in the manufacturing process and day-to-day operation. During the production of x-ray systems, personnel follow strict procedures to keep the risk of accidental exposure as low as possible. When a system is complete, it is tested for radiation leakage as part of the quality control process.

An additional radiation test is performed after installation to verify that no damage occurred during transport or installation. After installation, operators must follow the safety procedures that are in place. These procedures include:

The correct method for removing products from the system in the event of a jam or conveyor malfunction
The proper cleaning procedures
Appropriate handling and removal of rejected products

They also include routine system maintenance, since keeping the system functioning properly is the best way to keep x-ray exposure as low as reasonably achievable.

Depending on local regulations, periodic or annual radiation surveys of the production site may also be required. Local radiation guidance and regulatory requirements vary by country, so operators should always follow the specific rules and procedures applicable in their location. This is an effective way to verify the safety of the system throughout its operational lifespan.

ALARA does not apply only to the use of x-ray inspection systems in production, it also applies to the manufacturing of the systems themselves. All handling of the components that make up an x-ray generator and system is carried out to minimize the risk of radiation exposure.

Regular radiation surveys are conducted to verify the integrity of the system hardware and ensure that no radiation leaks go undetected. As an added safety measure, production personnel wear dosimeters as systems are assembled. Dosimeters monitor radiation exposure and help verify that the safety measures in place are working as intended. Some manufacturers also require personnel who operate x-ray inspection systems to wear dosimeters as an additional safety measure, but this is not a requirement in all cases.

One of the most important things to keep in mind when considering radiation exposure in manufacturing is how minimal it is. The average operator of an x-ray inspection system is unlikely to be exposed to x-ray radiation at all, thanks to cabinet shielding.

The most likely points of radiation leakage in an x-ray inspection system are where products enter and exit the system, areas where operators are not typically standing. In addition, operators are not likely to be near the system at all for most of their shifts. Combined with other reasonable safety measures, maximum exposure to radiation can remain well below 1 µSv/hour.

X-ray inspection systems are used to help keep consumers safe from foreign body contamination, and their construction and operating procedures are designed to help keep operators safe from radiation exposure. There is no way to avoid exposure entirely, but by keeping the risk of exposure as low as reasonably achievable, operators can continue their routines with confidence.

Learn more about x-ray safety in food production in our white paper “How Safe is X-ray Inspection of Food?”

ALARA’s principles of risk reduction can be expanded into a general workplace health and safety philosophy. Instead of ALARA, or As Low As Reasonably Achievable, this becomes ALARM: As Low As Reasonably Manageable.

A contamination control plan has three goals: eliminate contamination, prevent contamination, and detect contamination if elimination and prevention fail. The first two goals, elimination and prevention, are process-based. By “processes,” we mean cleaning routines, line equipment such as magnets or sieves, and daily operating procedures. This also includes how frequently systems are cleaned, how employees are expected to dress, and the use of personal protective equipment (PPE) such as hairnets, masks, and gloves. It also includes system maintenance to prevent contamination caused by failing equipment, such as metal or plastic shavings.

The third goal, detection, is needed when the first two goals fail and depends entirely on inspection equipment. Manufacturers must determine the most effective location on the production line for inspection equipment. This location may vary depending on the product type and production line layout, but in general there are three points to consider on a production line:

Front end of production
In-process
End-of-line

Placing a system at the end of the line may seem like the best way to verify that the finished product is free of contaminants, but in the case of metal contamination, it may damage downstream production equipment. Waiting until the end of the line to find contamination can also increase product waste, since the product will already be fully packaged and ready to ship rather than still in process. For this reason, manufacturers must conduct a thorough risk analysis to determine the best points in the process for placing control points. Depending on cost, a manufacturer may decide to place systems at multiple points on the line, or just one.

As an example of how ALARM uses ALARA as the basis of a contamination detection strategy, consider contaminant size. The goal is to remove contaminants that pose a significant risk to consumer safety, while also balancing practicality and cost. Most food safety standards or codes of practice define the size of contaminant that must be detected, but some leave that decision to the manufacturer. Depending on the contaminant, the allowable size may vary as well. For example, a small fragment of glass is dangerous regardless of size, whereas a small bone fragment is less of a concern. Therefore, food manufacturers set detection limits that minimize risk while also considering cost and the impact on production efficiency. This helps keep the risk of dangerous contamination as low as reasonably manageable.

Ultimately, the goal of ALARM is to help manufacturers keep people safe, from production personnel to consumers. While the acronym is most often associated with the safe construction and operation of x-ray equipment, it is a framework that can also be applied to broader topics such as consumer safety. Approaching issues of safety with the goal of keeping risk as low as reasonably achievable helps manufacturers maintain product safety without incurring unnecessary costs or using impractical designs.

METTLER TOLEDO Product Inspection solutions are built on this same philosophy. As an experienced partner, METTLER TOLEDO helps food manufacturers build and improve their food safety programs. This includes assistance with identifying critical control points on the production line, determining the level of sensitivity needed in detection equipment, and selecting the right inspection technologies for each application. METTLER TOLEDO supports manufacturers by delivering solutions that balance reliability, efficiency, and cost-effectiveness, helping keep the risk of production and product quality issues as low as reasonably manageable.

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Adam Green

客戶解決方案經理，METTLER TOLEDO Product Inspection（X-ray Inspection）

Adam 在 METTLER TOLEDO 擔任過各種商務與技術職務，至今已超過十年。在這段期間，他協助開發了一個線上示範平台，為全球客戶提供技術支援。他與當地業務團隊及外部客戶合作，推廣 x-ray inspection 技術在食品與製藥產業中的優勢。他也支援提升客戶在 METTLER TOLEDO 各項服務中的參與度。

建議搜尋

ALARA Principles: Helping Keep Consumers and Producers Safe

Using the framework of ALARA to build a broader food safety philosophy

ALARA and ALARP

Cabinet X-ray Systems

How Radiation Is Measured

Time, Distance, and Shielding

The materials that make up the cabinet are one part of minimizing radiation exposure, but two other important factors are also involved: distance and time.

How Exposure Is Calculated

X-ray Inspection System Safety

Additional Safety Steps

ALARA Keeps Exposure Very Low

ALARA Becomes ALARM for Food Safety