🌿 Exposure to visible and infrared radiation from artificial sources at the workplace — measurement in the band 380 nm – 3 µm and assessment of the blue light hazard (300–700 nm)

Environment PN-EN 14255-2

Overview

The standard specifies procedures for the measurement and assessment of the exposure of persons to visible (VIS) and infrared (IR) radiation emitted by artificial sources wherever harmful effects cannot be excluded in advance — with the reservation given expressly in the scope of the standard: such effects usually do not occur in exposures caused by the normal lighting or heating of rooms. It is applied at workplaces inside and outside buildings, it is not applied to exposure during leisure time, nor to solar radiation, nor to coherent sources, that is lasers, nor to the emission of radiation from products (those are described by EN 12198 for machinery, EN 60335-2-27 for domestic appliances, CIE S009 for lamps), nor to thermal load understood as the long-term action of heat. Neither does it cover effects whose action spectra lie exclusively in the ultraviolet region 180–400 nm — that is dealt with by Part 1.

The fundamental difference with respect to Part 1 lies in the band and in what is measured. The spectral range is 380 nm – 3 µm, and in addition 300–700 nm for exposures which may constitute a blue light hazard; that band therefore formally covers part of UV-B and the whole of UV-A, although the hazard connected with it is commonly called the „blue light" hazard. Whereas in ultraviolet radiation the effective radiant exposure of the skin and the eyes is assessed, here the leading quantity is often the effective radiance of the source — and then the result is decided by two things which are not present in Part 1: the angle of view of the source α and whether the total or the single exposure time counts. The total time is determined for the photochemical blue light hazard, the single time — for the thermal hazards to the eye and the skin from VIS, IR-A and IR-B radiation.

Like Part 1, the standard does not lay down exposure limit values: it supports the application of the values laid down by national regulations or by international recommendations. The structure of the document is the same — the general procedure, the preliminary survey, the analysis of the work task, the measurement of the exposure (planning, the quantities to be determined, the choice of the method, the requirements for the measuring methods, the performance, the presentation of the results), the assessment of the exposure, the decision on protective measures, the repetition of the measurement and the assessment and the report in a short and a full version. The informative annexes contain a block diagram of the procedure, example tables for the analysis of the work task, a survey of the instruments commonly used for measuring radiation, examples of protective measures and examples of methods of determining the quantities Lr, Lb, Gb, Hb, Eb, E and H together with the assessment of the hazards connected with them.

The Polish context fills in what the standard deliberately does not give. The bands are VIS 380–780 nm, IR-A 780–1400 nm, IR-B 1400–3000 nm, IR-C 3000 nm – 1 mm. The photochemical hazard to the retina is assessed for the band 300–700 nm: for large sources (α ≥ 11 mrad) the MDE is LB = 10⁶/t [W·m⁻²·sr⁻¹] at an exposure time t ≤ 10 000 s and LB = 100 [W·m⁻²·sr⁻¹] at t > 10 000 s, and for small sources (α < 11 mrad) respectively EB = 100/t [W·m⁻²] and EB = 0.01 [W·m⁻²]. The thermal hazard to the retina is assessed for the range 380–1400 nm for sources of high brightness, that is of a luminance greater than 1 cd/cm² (10 000 cd/m²), by determining the effective radiance LR taking into account the spectral effectiveness R(λ) and the dimensionless factor Cα depending on the angle of view. The thermal hazard to the cornea and the lens is assessed for the range 780–3000 nm on the basis of the total irradiance EIR: EIR = 18 000·ti⁻⁰·⁷⁵ W·m⁻² for a single exposure time ti < 1000 s and EIR = 100 W·m⁻² for ti ≥ 1000 s. The thermal load of the skin is assessed over the whole range 380–3000 nm where ti < 10 s, with the condition Hskin ≤ 20 000·ti⁰·²⁵ J·m⁻².

Method principle

The procedure has the same seven-step skeleton as Part 1 — preliminary survey, analysis of the work task, measurement, assessment, decision on protective measures, decision on repetition and report — but the quantities measured are different. For the photochemical blue light hazard to the retina the effective radiance LB (large sources, α ≥ 11 mrad) or the effective irradiance EB (small sources, α < 11 mrad) is determined, weighting the spectrum with the spectral effectiveness function of photochemical damage B(λ) and measuring the total exposure time. For the thermal hazard to the retina the effective radiance LR is determined in the range 380–1400 nm with the function R(λ), at a single exposure time ti and an angle of view of the source α, on which the factor Cα depends. For the thermal hazard to the cornea and the lens the total irradiance EIR is measured in the range 780–3000 nm with a probe without spectral correction (a linear characteristic), of a spectral range coinciding with that required by the admissible values. The probe is placed at the height of the organ under consideration — the eye, the skin of the face or of the hand — for which the hazard is considered; when assessing the exposure of persons who move about, the measurements are carried out at the individual places where they are present. Besides the radiometric measurements, a measurement of the exposure time is necessary (the total one for the photochemical hazards, the single one for the thermal ones) and the determination of the angle of view of the source α. The values obtained are compared with the limit values from the national regulations — the standard does not lay them down itself.

Applications

• Metallurgical and heating furnaces, sintering, casting, rolling and forging of metals — the classic sources of infrared radiation of high irradiance
• Welding and arc processes — the arc emits, besides ultraviolet radiation, strong visible radiation, including blue light
• Infrared radiators: incandescent, ceramic and quartz, xenon lamps — drying, heating, heat treatment
• Offset drying units in printing, using short-wave infrared radiation IR-A
• Lamps for irradiating photosensitive layers and other sources of high brightness assessed for the hazard to the retina
• Periodic tests and measurements of harmful agents: at least once every two years at an exposure level above 0.4 up to 0.7 of the MDE value and at least once a year above 0.7 MDE

Key parameters

Standard

Standard number

PN-EN 14255-2:2010

Title (PL)

Pomiar i ocena ekspozycji osób na niespójne promieniowanie optyczne — Część 2: Promieniowanie widzialne i podczerwone emitowane przez źródła sztuczne na stanowisku pracy

Title (EN)

Measurement and assessment of personal exposures to incoherent optical radiation — Part 2: Visible and infrared radiation emitted by artificial sources in the workplace

Step-by-step procedure

1. Preliminary survey

   Collect information about the source and about the possible exposure and decide whether an assessment based on measurements is necessary. Measurements are not carried out if only light sources serving to light rooms or workplaces are operated, used in the luminaires intended for them and at an appropriate distance from the exposed parts of the body. The risk assessment may also be based on the data of the manufacturer — the risk group according to PN-EN 62471 or the emission category of the machine according to PN-EN 12198-1.

2. Analysis of the work task

   Set out the activities of the worker: where they stand, how long they look in the direction of the source, which parts of the body are uncovered, what the working cycle of the source is. From the analysis follow the places of measurement, the total and the single exposure time and the angle of view of the source.

3. Choice of the hazards to be assessed

   Establish which hazards come into play: the photochemical blue light hazard to the retina (300–700 nm), the thermal hazard to the retina (380–1400 nm, sources of a luminance greater than 10 000 cd/m²), the thermal hazard to the cornea and the lens (780–3000 nm), the thermal hazard to the skin (380–3000 nm where ti < 10 s).

4. Choice of the method and the instrument

   Choose a broadband radiometer with an appropriately corrected probe or a spectroradiometer, taking into account the limitations of the standard: a detector array is not recommended for blue light where α < 11 mrad, a scanning static spectroradiometer only for sources constant in time, and for the assessment of the thermal hazard to the skin in the range 380–3000 nm no kind of spectroradiometer may be used.

5. Measurement

   Place the probe at the height of the organ under consideration (the eye, the skin of the face or of the hand). For persons who move about, carry out the measurements at the individual places where they are present. Measure the radiometric quantities and — separately — the exposure time: the total one for the photochemical hazards, the single one for the thermal ones.

6. Determination of the effective quantities

   Calculate LB or EB taking into account the spectral effectiveness B(λ), LR taking into account R(λ) in the range 380–1400 nm together with the factor Cα depending on the angle of view of the source, EIR as the total irradiance in the range 780–3000 nm and the radiant exposure of the skin Hskin in the range 380–3000 nm.

7. Assessment

   Compare the results with the MDE values: for large sources LB = 10⁶/t at t ≤ 10 000 s and LB = 100 at t > 10 000 s, for small ones EB = 100/t and EB = 0.01; for the cornea and the lens EIR = 18 000·ti⁻⁰·⁷⁵ W·m⁻² at ti < 1000 s or 100 W·m⁻² at ti ≥ 1000 s; for the skin Hskin = 20 000·ti⁰·²⁵ J·m⁻² at ti < 10 s.

8. Protective measures, repetition and report

   Take a decision on protective measures — limitation of the exposure time, increase of the distance from the source, screening — and on the date of the repetition of the measurement: at least once every two years at a level above 0.4 up to 0.7 MDE and at least once a year above 0.7 MDE. Draw up a report; the standard provides for a short and a full report.

Required equipment and apparatus

Health and safety (OHS)

• The person carrying out the measurement looks in the direction of a source of high brightness — use filters and eye screens matched to the band of the source, also for short check measurements.
• The eyeball has no heat receptors warning against infrared radiation — the absence of a sensation of heat in the eyes does not mean the absence of exposure; the cornea signals pain only at a temperature of about 47 °C, and a burn of it may occur several degrees lower.
• The main effect of chronic exposure of the eye to infrared radiation is infrared cataract (smelters’ / glassblowers’ cataract), developing over a dozen or even several dozen years — protection makes sense also where nothing hurts.
• Photochemical damage to the retina accumulates over the whole day of exposure, and for that reason in the blue light hazard the total time counts and not a single glance.
• A measurement at metallurgical furnaces, at welding and at radiators means also a thermal hazard, spatter and fumes — apply the protective measures proper to that workplace, not only eye protection.
• Work in exposure to infrared radiation, in particular at metallurgical and heating furnaces and at the sintering, casting, rolling and forging of metals, is forbidden to juvenile workers.

Frequently asked questions