At the Forum: How clean will the 13th General Election be?, there was a request for information on preparation in case police again tear gas the participant.
Did a bit of searching and found this: Tear Gas Exposure
How to Deal with Tear Gas.
Some of the tips was to bring a bandana (large hankerchief/scarf) soaked with lemon juice or vinegar and breath though it. Wash tearing eyes with saline (salt) solution (bring salt and water). Bring tight fitting swimming googles.