The investigations performed on laser printers essentially served as a revision of the test method for the determination of emissions from hardcopy devices for the envi-ronmental award "Blue Angel" for office devices according to RAL-UZ 62, 85 and 114 of June 2003. The resulting test procedure according to RAL-UZ 122 was previously published in June 2006.
The changes in relation to the test method of June 2003 are listed in the following:
Procedure according to RAL-UZ 122:
• Loading of the chamber on the day preceding the test
• Measurement of L*, a*, b* values without linearization of the grey tones
• Calculation of the emission rate for ozone takes place at the maximum con-centration during the first 10 minutes of printing
• Sampling for VOC in the follow-up phase only for the period of one air ex-change
• Sampling flow rate for VOC up to 200 ml/min
• Quantification of unknown substances using the response factor of toluene (previously: deuterated toluene)
• New calculation formula for the VOC emission rate of the printing phase
• VOC limit no longer considered as a concentration, but emission rate as a function of chamber size
• Additional data in the test report, in particular a new form
• New colour template (www.ps.bam.de/RALUZ122)
• Manufacturer’s adjustment instead of maintaining of the pre-operating phase beyond 60 min,
• Approval of UV devices for ozone determination
• Determination of ozone half-life at low ozone emissions is void
• Additional sampling using Carbosieve or Carbotrap for benzene determination
In addition to amending the test method, new maximum emission values were speci-fied for the assignment of the environmental label RAL-UZ 122 of the Federal Envi-ronment Agency in co-operation with BAM based on the measurement results on colour laser printers. These new maximum values can be found in Table 11.
Table 11: Permitted maximum emission rates per RAL-UZ 122
Substance Emission rate
Printing phase (mg/h)
Emission rate Pre-operating phase
(mg/h).
Colour print Sum Pre-operating + printing phase
Monochromatic print Sum
Pre-operating + printing phase
Desktop devices
Freestanding devices (Device volume
>250 litres)
TVOC 18 10 1 2
Benzene < 0.05 < 0.05
Styrene 1.8 1.0
Ozone 3.0 1.5
Dust 4.0 4.0
The report presents the emission test results of VOC, ozone and dust on more than 70 different printers and copiers. The preliminary investigations deal with the tests from the years 2003 to 2004, and the main investigations describe the tests per-formed in 2005 and 2006, in particular those on colour laser printers.
The maximum value specified by the Blue Angel for the dust emission rate of 4 mg/h, was not exceeded in any of the cases.
While the maximum value for ozone emission (2 mg/h as per RAL-UZ 114 and 1.5 mg/h as per RAL-UZ 122) was not exceeded by desktop devices, it was ex-ceeded by some of the freestanding devices.
VOC emissions are also higher on average from freestanding devices than from desktop devices. This can be explained by a larger equipment mass and surface of freestanding devices. The calculation of TVOC emission rates according to RAL-UZ
114 at higher pre-operating emissions in the printing phase yielded higher emission rates than is the actual case in the printing process. Therefore a new calculation for-mula was established for RAL-UZ 122. The application of this new forfor-mula leads to markedly lower VOC emission rates in the printing phase of devices which exhibit a relatively high pre-operating emission in comparison to RAL-UZ 114.
It is noticeable that some of the colour printers exhibited similar TVOC emission rates in the colour printing phase as in monochromatic printing, although the paper cover-age of 20 % is four times as high and thus toner consumption is also considerably higher. Apparently, some coloured toners contain much less VOC than black toners.
When comparing test devices which were used frequently, or on a daily basis, to those which were only used in the tests, a markedly stronger decrease in the TVOC emission rate was found over a 2-month period, while the ozone emission rate hardly changed.
A good reproducibility of ozone emission was found when the agreement of meas-urement results from identically designed devices was investigated. However, the TVOC emission rate could vary sharply due to the use of toner cartridges from differ-ent production batches. This also applied to individual VOCs.
A proportional relationship between printing rate and TVOC emission rate has not been found. On the average a higher lightness L* may be the explanation, i.e. a more moderate blackening in the case of faster printers. Faster printers thus use less toner per page, whereby a potential VOC emission is reduced.
The investigations performed for dust characterisation unfortunately furnished no ex-plicit results. Although toner particles could be detected on the glass-fibre filters, dust sampling has so far not been able to detect paper dust on the glass-fibre filters. Thus no conclusions have been possible as to the fraction of paper dust in total dust emis-sion.
The use of particle spectrometers for particle counting confirmed that ultra fine dust emerged in the laser printing phase. Very different particle spectra with changing
par-ticle size as a function of time were found in the tested laser printers. A chemical characterisation of the ultra fine dust has so far not been possible. The toner, the pa-per or VOC/SVOC emissions may be potential sources of nanoparticles. Further tests are necessary for a more exact characterisation of the fine and ultra fine dust parti-cles.
For this purpose methods are needed to size-classify and separate the ultra fine par-ticles and enable an access to further physical and chemical analyses.
All in all, emission measurements of ultra fine particles from laser printers are clearly reproducible in an emission test chamber both quantitatively and as a function of time.
However, further research is needed for the integration of particle counting into the emission test method according to RAL-UZ 122 and for the specification of limiting values for particle emissions addressing the following issues:
• Comparability of measurements using different particle counters (measure-ment principles, sample flow rates, measure(measure-ment ranges)
• Measurements in different emission test chambers (chamber volume, air ex-change rate, air flow, background concentration, climate)
• different methods for the evaluation of assumed data (determination of emis-sion rates, particle number concentrations, particle mass concentrations, total particle emissions)