Very bad and so wide in variety depending on agent(s) used that I have no hope of even beginning to enumerate them here - even if I spent a whole week doing nothing but typing them. Sorry. I will give a short list:
- Irritant gasses: hard to breath, coughing, usually not fatal.
- Blister agents: blisters everywhere including lungs, usually fatal pneumonia.
- Nerve agents: seizures followed by death.
- Hallucinogen gasses: hallucinations, paranoia, often attacks and kills friendlies in his confusion. Likely to recover.
- Vomiting gasses: disables by causing continuous vomiting for hours. May survive with medical treatment.
- Biological agents: causes disease of choice by creator.
- Immunological agents: causes mild flu like disease. When you recover your immune system has been immunized against you. Your own immune system then proceeds to kill you. (The USSR actually designed, made, and tested one of these in the early 1980s. Look up Ken Alebek on the net, he was the head scientist on the project and now works in CA for a private genetic engineering company.)