Context : Star formation activity is an important driver of galaxy evolution and is influenced by the physical properties of the interstellar medium .
Dwarf galaxies allow us to understand how the propagation of radiation and the physical conditions of the different ISM phases are affected by the low-metallicity environment .

Aims : Our objective is to investigate the physical properties of the ionised gas of the low-metallicity dwarf galaxy , IC 10 , at various spatial scales : from individual H ii regions to the entire galaxy scale and examine whether diagnostics for integrated measurements introduce bias in the results .

Methods : We modeled the ionised gas combining the mid- and far-infrared fine-structure cooling lines observed with Spitzer /IRS and Herschel /PACS , with the photoionisation code Cloudy .
The free parameters of the models are the age of the stellar cluster , the density and the ionisation parameter of the ionised gas as well as the depth of the cloud .
The latter is used to investigate the leakage of the ionising photons from the analysed regions of IC 10 .
We investigate H ii regions in the main star-forming body , on scales of \sim 25 pc , three in the main star-forming region in the center of the galaxy and two on the first arc .
We then consider larger sizes on the scale of \sim 200 pc .

Results : Most clumps have nearly identical properties , density \sim 10 ^ { 2. } - 10 ^ { 2.6 } cm ^ { -3 } , ionisation parameter between 10 ^ { -2.2 } and 10 ^ { -1.6 } and age of the stellar cluster \sim 5.5 Myr .
All of them are matter-bounded regions , allowing ionising photons to leak .
The relatively uniform physical properties of the clumps suggest a common origin for their star formation activity , which could be related to the feedback from stellar winds or supernovae of a previous generation of stars .
The properties derived for \sim 200 pc size ” zones ” have similar properties as the H ii regions they encompass , but with the larger regions tending to be more radiation-bounded .
Finally , we investigate the fraction of [ CII ] 157.7 \mu m , [ SiII ] 34.8 \mu m and [ FeII ] 25.9 \mu m emission arising from the ionised gas phase and we find that most of the emission originates from the neutral gas , not from the ionised gas .

Conclusions :