Can I delete .dmg files off my iMac?

Well, the short version of the question is in the title, but I'll explain further. My iMac, my families main computer, is running out of disc space, and after googling/looking for topics on the issue, I still can't find a clean cut answer to the question "If I delete .dmg files for programs I have already install/use, will the programs become unusable/broken and will my iMac still function properly?". I ask this because, as I said, I'm running out of space and there isn't much else to delete, and I noticed the .dmg files have been taking up a ton of data. I obviously won't just delete all of them willy-nilly, but I mean can I delete ones for updates to Safari or Firefox or iTunes, or even ones for one-time downloads like MSN? Thanks in advance, I just want to be sure on the issue, so far it seems like I safely can if I have installed the application to the applications folder.