No. 104 - Miljøstyrelsen

28
time unit, but this formula (as illustrated with the graph above) only applies to
the average content of mercury of 4.55 mg of mercury per straight fluorescent
lamp.
Stahler et al. (2008) has also made measurements of release of mercury from
compact fluorescent lamps in a room of around 12.7 m 2
and with a floor-toceiling
height of around 3 m 2 , corresponding to a volume of around 39 m 3 .
The tests were made with different lamps, flooring, ventilation scenarios and
cleaning scenarios. Many different tests were made, but one lamp was broken
at a time after which a new test (new lamp with new flooring material etc.)
was analysed. The concentration of mercury was measured at a height of
around 30 cm (corresponding to the inhalation height of a child) and at a
height of around 1.5 m (corresponding to the inhalation height of an adult).
To simulate worst case new compact fluorescent lamps were broken with a
hammer, and measurements showed a tendency to higher concentrations at
30 cm height than at 1.5 m height in tests without vacuuming. This reflects
that mercury vapours are very heavy and concentrate near the floor. The tests
showed that when one compact fluorescent lamp broke mercury
concentration in the air of the room often exceeded 0.0003 mg Hg/m 3
for a
period of time (corresponding to the USEPA reference long-term
concentration without hazardous effects (RfC)). Short fluctuations with
concentrations above 0.05 mg/m 3 (upper measurable limit) were also
registered. In comparison, Danish occupational threshold limit values for
mercury vapours are at 0.025 mg Hg/m 3
during a workday (AT, 2007).
It was seen, however, that a short period of ventilation of the room (open
window) in most cases reduced the mercury concentration significantly, both
in 30 cm’s height and in 1.5 m’s height. For all tests (a total of six) the
concentration in 30 cm’s height decreased to below 0.0003 mg Hg/m 3 within
9½ minutes after breakage of the lamp. Concentrations increased again,
however, when the room was no longer ventilated, especially for some types of
lamps as well as during and after vacuuming. Measurements showed that
there are large differences between different types of compact fluorescent
lamps, and between the period of time before mercury concentrations
decrease to below 0.0003 mg/m 3
.
One test was also conducted with a cracked lamp instead of a broken lamp as
well as one test where lamps were warm further to use. The results from these
tests were similar to results from previous studies (Stahler et al., 2008).
The main conclusion of the Stahler et al. (2008) study was that the release of
mercury vapour is much more variable for scenarios with compact fluorescent
lamps from different manufacturers than between different accident and
cleaning scenarios with compact fluorescent lamps from the same
manufacturer. In other words, release of mercury depends more on type of
lamp, i.e. especially quantities of mercury in the lamp and it may also depend
on the mercury compound found in the lamp. In the study six different
brands of compact fluorescent lamps with different effect were used so results
from the study are assumed to represent a general picture if a compact
fluorescent lamp should break in a home.
Stahler et al. (2008) is concerned about postponing cleaning after an accident
with a broken compact fluorescent lamp. Three tests were made with exactly
the same type of lamp, but with cleaning after 1 minute and 46 minutes after
the accident. It was seen that even if the initial mercury concentration was the