Context : Dust properties are very likely affected by the environment in which dust grains evolve .
For instance , some analyses of cold clumps ( 7 K- 17 K ) indicate that the aggregation process is favored in dense environments .
However , studying warm ( 30 K-40 K ) dust emission at long wavelength ( \lambda > 300 { \mu m } ) has been limited because it is difficult to combine far infrared-to-millimeter ( FIR-to-mm ) spectral coverage and high angular resolution for observations of warm dust grains .

Aims : Using Herschel data from 70 to 500 { \mu m } , which are part of the Herschel infrared Galactic ( Hi-GAL ) survey combined with 1.1 mm data from the Bolocam Galactic Plane Survey ( BGPS ) , we compared emission in two types of environments : ultra-compact HII ( UCHII ) regions , and cold molecular clumps ( denoted as cold clumps ) .
With this comparison we tested dust emission models in the FIR-to-mm domain that reproduce emission in the diffuse medium , in these two environments ( UCHII regions and cold clumps ) .
We also investigated their ability to predict the dust emission in our Galaxy .

Methods : We determined the emission spectra in twelve UCHII regions and twelve cold clumps , and derived the dust temperature ( T ) using the recent two-level system ( TLS ) model with three sets of parameters and the so-called T- \beta ( temperature-dust emissvity index ) phenomenological models , with \beta set to 1.5 , 2 and 2.5 .

Results : We tested the applicability of the TLS model in warm regions for the first time .
This analysis indicates distinct trends in the dust emission between cold and warm environments that are visible through changes in the dust emissivity index .
However , with the use of standard parameters , the TLS model is able to reproduce the spectral behavior observed in cold and warm regions , from the change of the dust temperature alone , whereas a T- \beta model requires \beta to be known .

Conclusions :