How can I test whether Chromium is running inside sandbox

I am using Chromium browser on Debian Wheezy. I read that Chromium is using sandbox to isolate its processes from the rest of the system and thus to increase security. How can I verify that Chromium is indeed running inside a sandbox? Is Chromium using sandbox by default, or do I have to configure it? When I start Chromium by clicking on the icon, and then look at the running process with ps, I see no indication that it runs in sandbox (i.e. no --sandbox parameter).