Safety First: TP(a) Fire Ratings in UGR<19 Prismatics Diffusers
When selecting lighting for commercial spaces, offices, or educational facilities, achieving a low Unified Glare Rating (UGR<19) is often the top priority for visual comfort. However, there is a critical safety specification that often sits in the fine print but carries equal weight: Fire Safety Regulations.
For lighting manufacturers, understanding the difference between Polycarbonate (PC) and Polystyrene (PS) materials and how they achieve TP(a) classification is essential for compliance with building codes.
In this post, we break down the fire rating performance of two key prismatic materials based on recent laboratory tests.
What is TP(a) Classification?
Under the Building Regulations 2010, Approved Document B (Fire Safety), lighting diffusers are classified based on their burning behavior.
TP(a) Rigid is the highest classification for thermoplastic lighting diffusers. To achieve this, a material must demonstrate that:
1. The test flame extinguishes before reaching the first mark (25mm) during testing.
2. Alternatively, the duration of flaming or afterglow does not exceed 5 seconds following the removal of the burner.
We recently commissioned independent testing by SGS to see exactly how our Prismatic Diffusers perform under these rigorous conditions. Here is how both materials stood up to the heat.
Test Standard: BS 2782-0:2011 Method 508A.
Official Classification: TP(a) rigid.
\We offer 2 materials TP(a) rated: Polystyrene in special grade, and the regular Polycarbonate.
Polystyrene (PS)
Polystyrene is often chosen for its cost-effectiveness and excellent optical clarity. Historically, PS struggled with fire ratings compared to PC, but advanced formulations now allow high-quality PS prismatics to achieve the required safety standards.
The Results: The PS samples performed flawlessly against the TP(a) criteria. Similar to the PC version, the flame front did not pass the 25mm mark.
Polycarbonate (PC)
Polycarbonate is renowned for its impact resistance and thermal stability. Our recent testing confirms its robust safety profile for lighting applications.
The Results: During the test, the PC specimens showed exceptional resistance. The flame did not travel to the 25mm mark, and critically, there was 0 seconds of afterflame or afterglow once the burner was removed.
Final Thoughts
Achieving a UGR<19 glare rating shouldn’t come at the expense of safety. Whether your project requires the mechanical strength of Polycarbonate or the specific optical properties of Polystyrene, both the Poly Series and S Series are verified to meet the TP(a) fire safety classification.
Using the TP(a) formula we can custom produce in various other types:
- Other types of prisms (Hexagonal, Micro Hexagon, etc)
- Other transmittance levels (From 50% to clear)
This means you can specify either material with confidence, knowing they comply with the stringent requirements of Building Regulations.