Hello. The stagger storm page on the wiki reads:

The following damage values represent the weapon at its completed level, without any UV or bonus from other equipment, and listed as a range found from the first to last floor of each stratum. The charge attack deals a small blast of Elemental damage upon detonation, then leaves an area of haze that causes Fire. The initial blast radius is considerably smaller than the haze's radius. Enemies that enter the haze are ignited and receive fire damage which is applied several times before the status wears off.

Here is a link to the page: http://wiki.spiralknights.com/Stagger_Storm

Thanks.