RF Safety in Industrial Drying, Defrosting and Heating Systems: How Strayfield Sets the Global Benchmark
Radio Frequency (RF) technology has become a proven, industrial-scale solution for drying, post-baking, defrosting, and disinfestation. Yet one question continues to surface—especially from safety officers and plant managers:
Is RF safe for people working around the equipment?
The short answer is yes—when the system is engineered, shielded, and validated correctly. This is where design discipline, global standards, and third-party verification make all the difference.
Understanding RF Radiation and Human Exposure
RF dryers operate in the non-ionising radiation spectrum. Unlike ionising radiation (Xrays, gamma rays), RF energy does not alter DNA or cause cellular damage. Its primary biological effect is thermal—the same principle used safely in everyday technologies such as radio broadcasting, Wi-Fi, and medical diathermy.
Electromagnetic spectrum illustrating radio frequency (RF) radiation in the non-ionising,
low-energy range, distinct from ionising radiation such as X-rays and gamma rays
Potential risks only arise if:
- Exposure levels exceed regulated limits, or
- Equipment allows uncontrolled leakage due to poor shielding or construction.
This is why international exposure limits exist—and why compliance must be proven, not
assumed
How Safety Limits Are Established Globally
Human RF exposure limits are defined using decades of biomedical research and conservative safety margins. Three globally recognised frameworks govern industrial RF equipment:
1. ICNIRP 2010 (International Standard)
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) sets exposure limits adopted by regulators across Europe, Asia, Australia, and beyond.
These limits:
- Differentiate between general public exposure and occupational exposure
- Include wide safety margins below any known biological effect
- Are designed for continuous, long-term exposure scenarios
For a detailed explanation of RF exposure limits and safety principles, visit the official ICNIRP website to read their radiofrequency guidelines in full: https://www.icnirp.org/en/frequencies/radiofrequency/index.html
2. SAR and Biological Protection Principles
In consumer electronics such as mobile phones and wearables, RF safety is commonly assessed using Specific Absorption Rate (SAR), which measures how much RF energy is absorbed by human tissue.
SAR (Specific Absorption Rate) limits for the head, torso, and limbs of a human figure, with specific values in W/kg and averaging masses.
In industrial applications like RF dryers, SAR is not the most practical metric due to distance and operating conditions. Instead, safety is evaluated using:
- Electric and magnetic field strength
- Induced currents in limbs
- Contact currents at accessible surfaces
While the measurement methods differ, the underlying biological protection principles are the same. Compliance with ICNIRP-based exposure limits inherently ensures SAR-equivalent safety margins, meaning exposure remains far below any threshold of biological concern.
Simply put:
If a system meets occupational RF exposure limits, it is operating far below any
threshold of biological concern.
3. National Regulations and Local Compliance
ICNIRP guidelines form the global scientific basis for RF safety, while individual countries adopt these principles into their own enforceable national standards. Although regulations and authorities vary by region, the underlying exposure limits remain closely aligned worldwide.
Strayfield RF systems are designed to comply with both international guidelines and applicable national regulations, ensuring safe deployment across global markets.
Understanding Occupational RF Exposure Limits
Industrial RF dryers fall under Occupational Exposure—defined as exposure:
- During controlled working conditions
- For trained personnel
- Within defined working hours
International occupational exposure limits for radiofrequency (RF) radiation, defining safe levels for electric fields, magnetic fields, and induced currents in industrial environments.
An independent third-party EMF and radiation safety assessment, conducted externally on an operating Strayfield RF system, defines the applicable occupational exposure limits at the machine’s operating frequency of 27 MHz.
The assessment evaluates exposure against clearly established thresholds for:
- Electric and magnetic fields
- Induced limb currents
- Contact currents
These occupational limits are set higher than general public limits to reflect controlled industrial environments, where trained operators follow defined procedures, access controls, and safety protocols. Even so, the limits remain deliberately conservative and are designed to provide a substantial margin of safety during normal operation.
What Independent Testing of the Strayfield Machine Actually Showed
A third-party EMF & Radiation Safety Survey, conducted by an ISO/IEC 17025 accredited laboratory, measured RF exposure around a Strayfield RF dryer installed at an industrial food production facility
Key Findings (Real-World Operation):
Independent third-party testing measured radiation levels at around 52 locations across and around a Strayfield RF dryer, covering all accessible operator areas. Even at the highest recorded point, overall radiation exposure was about 41% of the general public safety limit, while magnetic field levels remained below 20% of the permitted limit.
52 measurement points around the Strayfield Dryer
| Parameter Measured | What Was Evaluated | Result vs Occupational Limit |
| Limb exposure (hands, arms, legs) | RF-induced current in limbs during normal operation | ~31% of the allowable occupational limit |
| Contact exposure | RF current when touching accessible conductive surfaces | ~57% of the allowable occupational limit |
| Measurement heights | Head, chest, waist, and legs | Represents real working conditions, not theoretical exposure |
| Overall safety margin | Combined evaluation across all measurements | Substantial safety margins confirmed during normal operation |
What this means: Even under normal operating conditions and at the closest accessible points, operator exposure remains well below regulated occupational limits, confirming a strong margin of safety in real-world use.
What Independent Testing of the Strayfield Machine Actually Showed
Meeting RF safety limits is not automatic—especially at industrial power levels (75–85 kW and above). This is where many of our competitors struggle.
The Core Challenge
RF energy will always try to escape through:
- Inefficient RF grounding mechanisms
- RF circuit topologies that over rely on grounding
- Poor panel joints
- Bolted or segmented enclosures
No amount of “after-thought shielding” can compensate for weak RF circuit and mechanical design.
The Strayfield Advantage:
Balanced Output (Double-Ended) Electrode Design
Strayfield RF dryers use a double-ended electrode design, also known as a balanced output design, where RF power is applied and returned through two opposing electrodes.
This balanced configuration allows the RF energy to flow evenly through the product and back to the source, rather than being dumped or wasted.
How this improves RF safety
Because RF energy is balanced and controlled, there is far less stray or excess power within the system. This helps:
- Reduce unintended RF leakage
- Return path of the power is directly connected to the source
- Keep emissions within defined safety and regulatory limits
By using a balanced, double-ended design, Strayfield improves not only efficiency and drying uniformity, but also overall RF safety — ensuring energy is used where it is needed, and not released where it shouldn’t be.
Fully Welded RF Architecture
Strayfield RF dryers are engineered with a fully welded steel enclosure, not bolted panels or modular shells.
Fully Welded Strayfield Defrosting and Textile Drying Machines ayfield Dryer
This delivers:
- Continuous RF containment with no leakage paths
- Uniform grounding across the entire machine body
- Long-term shielding integrity (no loosening over time)
This level of fabrication precision is extremely difficult to execute, especially at scale—but it is precisely why Strayfield systems consistently pass third-party EMF testing with wide safety margins.
Many competitors attempt to meet standards through:
- Add-on shielding
- Operational restrictions
- Safety disclaimers instead of engineering solutions
As shown in the image, power flows symmetrically through the load and returns cleanly to the source, resulting in minimal wastage and higher efficiency.
Safety Isn’t a Feature. It’s an Outcome of Engineering.
RF safety cannot be achieved through claims, marketing, or partial compliance.
It requires:
- Deep understanding of RF physics
- Precision fabrication
- Conservative design margins
- Independent, third-party validation
This is why Strayfield systems are installed in some of the world’s most safety-regulated food and industrial environments—and why independent surveys continue to confirm their performance.
Superior design. Fully welded construction. Verified safety. Not every manufacturer can achieve it—but Strayfield has and continues to do so.
