ABS are recalling all steel cartridges filled between the 1st September 2008 and the 15th April 2010. There is a chance that the canister manufacturer supplied ABS with a faulty product which could result in the airbag failing to activate.
On the German language news section of the ABS web site there is a product recall announcement which mentions that only steel cartridges are affected during the period 1st September 2008 and the 15th April 2010.
All canisters are marked with a small round white sticker that indicates filling date - if you are in possession with a suspect canister ABS are exchanging all canisters via your local retailer.
Although the information is provided in German only ABS are contacting all their registered customers regarding this matter.