Ultraviolet (UV) light is a powerful tool used in various industries, from fluorescent inspection in aerospace, insect control in food and healthcare settings, and disinfection in medical environments.
However, the wavelength of UV light plays a pivotal role in both its effectiveness and safety. Using the wrong UV light tubes can lead to process failures, costly recalls, and severe health risks. In this post, we explore the importance of wavelength in UV safety, drawing from a comparison of four different UV light tubes to highlight the consequences of incorrect choices.
Why wavelength matters in UV applications
UV light is categorised into three main ranges based on wavelength: UV-A (315 – 400 nm), UV-B (280 – 315 nm), and UV-C (100 – 280 nm). Each range has distinct properties, making it suitable for specific applications but also posing unique safety risks. For instance:
- UV-A is commonly used for fluorescent inspection and insect control due to its relatively lower energy.
- UV-C, with its shorter wavelengths, is highly effective for disinfection but poses greater risks to skin and eyes, with safe exposure times often measured in seconds.
Selecting the wrong UV tube – and we’ve seen it happen more often than we’d have liked – whether due to cost-cutting or lack of knowledge can result in ineffective processes or dangerous overexposure. Let’s examine the consequences through real-world applications and a detailed comparison of four UV tubes.
Applications and risks of incorrect UV sources
Fluorescent inspection
In industries like automotive and aerospace, UV-A light is used for critical quality control processes, such as detecting oil leaks or cracks in components. These processes require a minimum UV irradiance level to ensure accuracy. However, installing incorrect UV-A tubes (e.g., with insufficient irradiance or the wrong wavelength) can compromise the process, leading to defective parts passing inspection. This has resulted in expensive product recalls and rework, far outweighing the cost of proper replacement tubes.
Insect control
Blacklight (BL) lamps, typically in the UV-A range (around 350 – 365 nm), are used to attract insects like wasps and flies into traps, particularly in food and healthcare settings. A critical error occurs when these lamps are mistakenly replaced with UV-C germicidal tubes. In one severe case, a maintenance engineer unknowingly installed germicidal tubes, leading to significant overexposure among kitchen staff, causing health risks due to UV-C’s harmful effects.
Disinfection
UV-C light (around 254 nm) is highly effective for disinfection, as it disrupts the DNA and RNA of microorganisms, preventing replication. However, its short wavelength makes it extremely hazardous, with exposure limits often exceeded in mere seconds. Incorrectly using UV-C tubes in place of UV-A or UV-B tubes can lead to serious safety violations.
Comparing four UV light tubes
To illustrate the impact of wavelength, we tested four UV light tubes of similar length (24″), and comparable wattage. Measurements were taken at a consistent distance of 15″ to assess UV irradiance and maximum permissible exposure (MPE) times for skin and eyes, as defined by The Control of Artificial Optical Radiation at Work Regulations 2010. The results, shown below, highlight stark differences driven by wavelength.
| Type | Type 1 | Type 2 | Type 3 | Type 4 |
|---|---|---|---|---|
| Manufacturer | Narva | Eiko | Sylvania | Philips |
| Wattage | 18W | 18W | 20W | 17W |
| Length | 24″ | 24″ | 24″ | 24″ |
| Peak Output | 365 nm | 365 nm | 350 nm | 254 nm |
| UV Range | UV-A | UV-A | UV-A | UV-C |
| Type | Blacklight blue | Blacklight blue | Blacklight | Germicidal |
| Primary Purpose | Inspection | Inspection | Insect Control | Disinfection |
| 365 nm Reading @ 15″ | 1,080 µW/cm² | 380 µW/cm² | 860 µW/cm² | 32 µW/cm² |
| 254 nm Reading @ 15″ | 0 W/m² | 0 W/m² | 0 W/m² | 19.75 W/m² |
| MPE @ 15″ (Skin) within an 8-hour period per day | 2 hours 20 minutes | 3 hours 40 minutes | 40 minutes | 3 seconds |
| MPE @ 15″ (Eyes) within an 8-hour period per day | 15 minutes | 30 minutes | 12 minutes | 3 seconds |
Key observations
- Type 1 and Type 2 (UV-A, 365 nm): Both are blacklight blue tubes designed for inspection. Type 1 delivers significantly higher irradiance (1,080 µW/cm²) than Type 2 (380 µW/cm²), making it more effective for fluorescent inspection. However, their MPE times for skin (2 hours 20 minutes and 3 hours 40 minutes) and eyes (15 minutes and 30 minutes) ensure safer exposure profiles compared to UV-C.
- Type 3 (UV-A, 350 nm): Designed for insect control, this tube has a shorter peak wavelength and lower MPE times (40 minutes for skin, 12 minutes for eyes), requiring stricter safety measures.
- Type 4 (UV-C, 254 nm): This germicidal tube emits high energy at 254 nm, resulting in extremely short MPE times (3 seconds for both skin and eyes). Its use in non-disinfection settings can cause immediate harm.
The spectral output of Type 4, concentrated in the UV-C range, explains its heightened risk. In contrast, Types 1-3 emit primarily in the UV-A range, which is safer but still requires adherence to exposure limits.
The importance of training and correct sourcing
The drastic differences in irradiance and MPE times underscore the need for proper training and sourcing of UV light tubes. Common mistakes include:
- Purchasing cheaper alternatives: Tubes may appear identical (same length, wattage, and fitting) but differ significantly in wavelength and output, leading to process failures or safety risks.
- Lack of expertise: Non-specialist suppliers may provide misinformation, resulting in incorrect tube selection.
- Inadequate training: Staff may unknowingly install harmful UV-C tubes in place of UV-A tubes, as seen in the insect control case.
To avoid these issues, organisations should:
- Consult the original equipment supplier, or a UV light specialist for replacement lamps.
- Train staff on UV safety and the differences between UV-A, UV-B, and UV-C.
- Regularly monitor UV irradiance and exposure times to ensure compliance with regulations.
Conclusion
Wavelength is a critical factor in determining the safety and efficacy of UV light applications. UV-A tubes (350 – 365 nm) are suitable for inspection and insect control but vary in performance, while UV-C tubes (254 nm) are effective for disinfection but pose significant health risks if misused. By understanding these differences and prioritising proper training and sourcing, organisations can prevent costly errors and protect their workforce.
Join us for a free UV Safety in the Workplace webinar to learn more about safe UV light practices.