A luminaire that lasts ten years in a clean workshop can fail within eighteen months in a washing room, an ATEX zone or a room at 90 °C. Neither the same products nor the same warranties. And since photometry there is less favourable than in offices, calculating beforehand is not a luxury: it is the only way not to get the quantity wrong.
What destroys a standard luminaire
Heat, from the inside as well as the outside
An LED does not burn out, it degrades: the higher the junction temperature, the faster the flux falls and the more the colour drifts. The weak link, however, lies elsewhere, in the driver and its capacitors. The rule of thumb in electronics is that about 10 °C more halves their lifetime. A luminaire stated at 50,000 hours at 25 °C ambient does not keep the same promise under a metal roof at 55 °C in August.
Cold poses symmetrical and less well-known problems: frozen electrolytes, difficult start-up, cyclic condensation, brittle plastics. A range stated from -60 to +120 °C does not mean that one model covers the whole range: it contains references dedicated to each end.
Water that gets in by breathing
A sealed luminaire is not hermetic. When switched on it heats up, the internal air expands and escapes; when switched off the pressure drops and it draws in ambient air through the slightest seal defect. This air is humid, dusty, sometimes loaded with chlorides, and the water ends up condensing on the electronics. It is the first cause of failure outdoors and in damp rooms, far ahead of LED defects. The remedy: a pressure compensation membrane and seals chosen for the environment.
Corrosion, rarely where you expect it
Aluminium dominates because it dissipates heat well, but it suffers in salt atmospheres, under ammonia in livestock buildings, under hydrogen sulphide in wastewater treatment plants. Corrosion almost always starts at a singular point: a stainless steel screw in an aluminium body, an unprotected seal groove, a hole drilled on site that destroyed the anodising. By the sea, marine-grade anodising or 316L stainless steel with compatible fasteners determines whether it lasts five years.
IP and IK: useful, but partial
They describe standardised tests on a new product, in a laboratory. Not ageing.
Rating | What it guarantees | What it does not say |
|---|---|---|
IP65 and IP66 | Dust-tight, resistant to water jets then powerful jets | Nothing about hot water, detergents, immersion or steam |
IP67 and IP68 | Temporary or prolonged immersion | An IP68 is not automatically IP66: separate tests, double marking required |
IP69 | High-pressure, high-temperature steam jets | Nothing about the chemical compatibility of cleaning products |
IK08 to IK10 | Impact of 5, 10 and 20 joules | Nothing about repeated impacts or permanent vibration |
A polycarbonate that is perfectly IP69 can crack on contact with certain alkaline detergents, and UV yellows exposed diffusers without any IP figure announcing it. As for corrosion, it is the salt spray test according to NF EN ISO 9227 that characterises it, and its duration in hours matters as much as its existence.
Hazardous area: the marking decides
In an explosive atmosphere, the question is no longer performance but authorisation. Zoning is established by the operator in its explosion protection document, under the Labour Code. The luminaire follows the zoning, never the reverse.
Gas zones range from 0 to 2 depending on whether the explosive atmosphere is present permanently, occasionally or rarely; dust zones follow the same logic from 20 to 22. Each zone corresponds to an equipment category under the ATEX directive 2014/34/EU and a type of protection within the meaning of the NF EN 60079 series.
- Ex d: flameproof enclosure. The explosion is allowed inside, the enclosure contains it and cools the gases. Hence massive bodies and thick glass.
- Ex e: increased safety, no ignition source allowed, reinforced connections.
- Ex m and Ex i: encapsulation in resin, or energy kept below the ignition threshold.
- Ex ec: zone 2 only. Ex t: protection by enclosure, the reference in dusty atmospheres.
A marking is read in full. On II 2 G Ex db IIC T4 Gb, the 2 designates the category compatible with zone 1, IIC the most demanding gas group, which includes hydrogen and acetylene, T4 a maximum surface temperature of 135 °C. For dust, the value is given directly, T85 °C for example. IIB equipment does not replace IIC, a T3 class does not cover a T4 need.
Two points remain underestimated. Certification covers the complete luminaire, cable glands included: drilling a body or changing a cable gland voids it. And installation as well as maintenance are standardised, parts 14 and 17 of the NF EN 60079 series: this is the aspect most often neglected during a lighting compliance audit. On the equipment side, the luminaires certified for ATEX zones from Rexylum, Luminance’s brand of professional LED luminaires, cover the common cases.
From -60 to +120 °C: everything depends on the ta range
Two values matter on a data sheet. The ta is the permissible ambient temperature range, the one that determines the warranty. The tc is the maximum temperature at the measuring point, required in hazardous areas. A product stated at ta -20 to +45 °C installed in a room at 60 °C works: it simply ages much faster, and outside the warranty. Hence the need to record the real temperature and not the annual average: the peak under the roof in summer, the value at luminaire height. In a cold room, it is the opposite: cold start, cyclic condensation, seals that stay flexible at -40 °C.
Three answers come up: the driver moved out of the hot zone; an oversized heat sink, reaching nominal flux at reduced current; documented derating with a chart of flux against ambient temperature. A manufacturer that does not publish this chart has not qualified its product over the whole range. The references designed for these environments are gathered in the Rexylum ranges for specialised sectors.
High-pressure washing and radiation
In food processing, the luminaire undergoes daily cleaning with hot water under pressure, alkaline detergent then acid rinse. Three requirements add up: a verified IP69, materials compatible with the products used, a geometry with no retention. A flat tempered glass diffuser and a 316L stainless steel body without sharp edges cost more to buy, and much less over five years.
Environments exposed to radiation are a separate case: ionising radiation colours transparent polymers, PMMA as well as polycarbonate, which brown and lose their transmission even before the electronics drift. The remedy combines a glass diffuser and electronics moved out of the zone.
Why photometry is harder there
A point rarely made: for the same power, a luminaire for harsh environments lights less well than a tertiary luminaire. The effects add up.
- Thick glass and protective grilles absorb part of the flux, from a few percent to more than fifteen depending on the model.
- Optics are fewer, especially in flameproof enclosures where very wide beams dominate: hard to target a specific workstation.
- Catalogue flux is measured at 25 °C. At 50 or 60 °C ambient, it is the derating chart that is authoritative.
- The maintenance factor drops: in a dusty workshop cleaned once a year, it most often falls to around 0.6 to 0.7, against 0.8 in a clean office. Yet NF EN 12464-1 imposes a maintained illuminance, that is, the end-of-cycle value, not the first-day value.
- Heights are great, often 8 to 15 m, and illuminance decreases with the square of the distance.
Replacing 200 old points with 200 new ones because the number is reassuring produces either under-lighting or over-investment. The only valid basis for the decision is the calculation, zone by zone, with real heights and reflectances, the right maintenance factor and the photometry of the products chosen. That is the purpose of a photometric study: checking the levels and uniformity required by NF EN 12464-1 indoors, NF EN 12464-2 outdoors and NF EN 1838 for emergency lighting. For halls and great heights, luminaires for great heights and industrial LED floodlights cover most cases, but the model is chosen after the calculation, not before.
In a harsh environment, the catalogue decides nothing. You start from the zoning, the real temperature and the cleaning protocol, you deduce the admissible product family, then you validate by calculation. In that order.
The checklist before ordering
- Official zoning and required marking: gas and dust, group, temperature class.
- Extreme ambient temperatures, measured at luminaire height, and cleaning protocol: pressure, temperature, products, frequency.
- Chemical atmosphere and mechanical constraints: salt, ammonia, solvents, vibration, access for maintenance.
- Photometric requirements by zone, glare, emergency lighting, real warranty conditions.
What a calculation made upstream changes
An example outside hazardous areas, but transferable. In an airport arrivals hall, the study brought 398 luminaires down to 315 points. Consumption went from €12,197 to €3,340 a year, a saving of €9,027 a year, for a budget of €27,405. Payback time: 37 months, €16,880 net over five years. The saving comes as much from the 83 points removed as from the efficacy of the sources. In a harsh environment, same logic with one more constraint: the product must last, otherwise the saving becomes a replacement budget.
The financing framework has changed. Since the order of 23 February 2026, in force since 25 February 2026, the CEE sheets BAR-EQ-110, BAT-EQ-127 and IND-BA-116 have been abolished: there is no longer any standardised bonus for indoor lighting, and any offer that promises one deserves careful examination. Outdoor lighting remains eligible through sheet RES-EC-104, revised by the order of 24 November 2025. Indoors, the levers are long-term leasing over three to five years, whose instalment is most often covered by the recorded saving, and the related items still eligible: building management systems, destratification, variable speed drives.
Having your site checked
Luminance Consulting has worked since 2013 on demanding industrial sites, from Arkema to BASF, from Safran to ArcelorMittal. The audit and the photometric study are free, site visit and 3D modelling included: Luminance is paid on the solution it supplies and has installed, not on the engineering. Describe your zones and constraints to us, then request a visit: you will know what will last on your site, with how many points and at what payback time.
