Materials and cleaning

The short answer

For most cleanrooms, a powder-coated steel body with a glass diffuser is a durable, easily cleaned choice. Laminated glass holds together if it breaks, which matters over open product and in food areas. Micro-prismatic PMMA gives better glare control and is lighter, but is more sensitive to some cleaning agents, so it is often placed behind glass. Stainless steel suits wet, corrosive or washdown areas. No material resists every disinfectant at every strength, so confirm resistance for the agents you actually use.

Diffusers: glass or PMMA

Diffuser	Strengths	Points to check
Hardened (toughened) glass	Hard, scratch-resistant surface that tolerates most cleaning agents. Breaks into small, blunt pieces rather than sharp shards.	If it does break, the pieces fall out. Not ideal directly over exposed product.
Laminated glass	Two sheets bonded with an interlayer, so broken glass stays in place. A good choice over open product and in food areas.	Slightly heavier. The edge of the interlayer should be protected from cleaning fluids.
Anti-reflective glass	A coating or etched finish that reduces reflections of the room and the LED points. Helps visual comfort and inspection.	Check that the coating suits your cleaning agents and cloths.
Micro-prismatic PMMA	Controls glare well (low UGR) and spreads light evenly. Light and shatter-resistant.	Softer than glass and can scratch. Some solvents and alcohols can cause stress cracking (crazing) in acrylics. Often supplied behind a glass cover for this reason.
Opal PMMA or polycarbonate	Soft, even appearance; shatter-resistant.	Same cleaning-agent caution as above, and lower light output than clear or prismatic optics.

A diffuser that combines micro-prismatic PMMA with a glass cover gives you the glare control of the prisms and a glass surface on the room side for cleaning.

Bodies: powder-coated steel or stainless steel

• Powder-coated steel is the usual choice for recessed cleanroom panels. A good-quality coating is smooth, non-porous and easy to wipe. It protects the steel only while it is intact, so chips and scratches should be avoided and repaired.
• Stainless steel suits wet rooms, washdown, food production and areas cleaned with chlorine-based agents. Grade 316, which contains molybdenum, generally resists chlorides better than grade 304. Even stainless steel can be marked or pitted by strong chlorine solutions left on the surface, so rinse after cleaning where the procedure allows.
• Aluminium frames are light and corrosion-resistant. Anodised or coated aluminium is common for diffuser frames.

Whatever the body, the room-side face should be smooth, with no exposed screw heads, open seams or ledges.

Frameless and framed faces

Frameless (flush) luminaires have the diffuser set into the body with no visible frame or fixings between them. The room-side face is close to a single smooth surface, so there are fewer edges where particles and cleaning residue collect, and wiping is quicker.

Framed luminaires hold the diffuser in a frame, often aluminium. They can be just as well sealed, but the step between frame and diffuser is one more edge to clean. For ISO 5 and cleaner, or wherever cleaning is frequent, frameless designs are often preferred. For ISO 7 to 9 and general hygienic areas, framed panels are widely used.

Cleaning agents and disinfectants

Clean areas use a range of agents, often in rotation. EU GMP Annex 1 asks for cleanroom materials to withstand repeated application of cleaning, disinfecting and sporicidal agents. Common types include:

• Alcohols (70% isopropyl alcohol or ethanol): fast-acting and widely used on surfaces. Generally fine on glass, steel and powder coatings. Can craze some plastics, including PMMA, especially under stress.
• Hydrogen peroxide, as a liquid or as vapour (VHP) for room decontamination: generally compatible with glass and stainless steel. Check gasket and plastic compatibility, and whether the luminaire should be switched off during fogging or vapour cycles.
• Peracetic acid blends: strong sporicides that can attack some metals, coatings and elastomers over time.
• Chlorine-based agents (sodium hypochlorite and similar): effective and low-cost, but corrosive to many metals, including some stainless steels, if left to dry on the surface.
• Quaternary ammonium compounds and detergents: common in food areas and for routine cleaning.

Resistance depends on the agent, its strength, contact time and how often it is used. Confirm resistance for each agent you use, at the strength you use it. Send us your cleaning schedule and we’ll ask the manufacturer to confirm compatibility for the body, diffuser, coating and gaskets. Where a datasheet doesn’t state resistance to a particular agent, we’ll say so rather than assume.

Food areas and glass

In food and drinks production, broken glass is a serious contamination risk. Food safety schemes such as BRCGS Food Safety expect sites to control glass and brittle materials, and lighting over exposed product is normally expected to be protected against breakage. Practical steps:

• Choose laminated glass or a shatter-resistant diffuser over open product, so a broken diffuser doesn’t drop fragments.
• Record every luminaire in the site’s glass and brittle materials register, with its diffuser type.
• Choose bodies and gaskets for washdown and your cleaning chemicals, with a room-side rating of IP65 or above.
• Avoid ledges on surface-mounted fittings where dust and moisture can settle.

How your scheme applies this is a matter for your HACCP plan and your auditor. We can supply diffuser and material details to support that, but we don’t certify luminaires against a food safety scheme.

How we can help

Tell us the room types, the cleaning agents and strengths you use, and whether there is exposed product, and we’ll suggest diffusers and bodies to suit. Start a project.

Sources: EudraLex Volume 4, EU GMP Annex 1 (2022), clauses 4.5–4.8; BRCGS Global Standard for Food Safety.