  Supernovae remnants are known to be luminous sources of infrared [FeII]
emission. By studying how the luminosity scales with age, environment and other
relevant factors, we can construct an [FeII] luminosity function for supernovae
remnants. This will enable us to predict supernovae rates in starburst galaxies
that are too distant for individual remnants to be resolved. First, however, we
require accurate luminosities for a sample of remnants of varying ages, and in
varying physical environments. As part of this project we have carried out an
initial study of a small sample of evolved (ages greater than a few thousand
years) remnants in M33. From these data we tentatively conclude that there is
evidence for the peak luminosity in the [FeII] lines of these sources to arise
in a narrow range of ages. In other respects, the M33 remnants are similar to
their galactic and Magellanic Cloud counterparts in the observed peak
luminosity. From this, and internal evidence as to the environment present in
these regions, we conclude that the luminosity of evolved remnants is only
marginally dependent on density and metallicity.
