Anyone has more information on this actions?On 3 September, a flight of German bombers dropped bombs containing sulfur mustard gas on a Warsaw suburb. Three years later the Third Reich claimed this had been accidental, and this is likely true. The Nazis certainly had no qualms about mass murder of civilians, and if they'd intended to use chemical weapons would no doubt have plastered the Polish capital with them. The Poles retaliated in kind at Jaslo in Galicia, where the German 136th Mountain Regiment encountered sulfur mustard mines placed to defend a key bridge crossing.
Conclusion
The action at Jaslo is the only confirmed instance of the intentional use of chemical weapons in the Second World War in Europe. Fourteen jägers suffered chemical burns and lung damage; the rest of the Tirolean regiment stormed the bridge and drove off the Poles. Higher command did not take the reports seriously, but the division staff decided that the Poles intended to wage this war with use of poison gas and instructed the troops to use their masks and protective gear at the first suspicious sign. This slowed the advance considerably — exactly the reaction the weapons were intended at achieve.
Also I would be interested in any information regarding Polish capabilities in chemical warfare.