If you have been exposed to toxic gas
If someone is having serious difficulty breathing or if they are unconscious, call 112. An unconscious person should be placed in the recovery position (turned slightly to the side, supported by bent limbs, face downwards). If the person is not breathing on their own, you may need to do cardio-pulmonary resuscitation or CPR. If you do not have first aid training, the SOS Alarm operator will tell you what to do. 112 can also put you in touch with the Swedish Poisons Information Centre ("Giftinformationscentralen"), which can answer questions about acute poisoning.
If the situation is not acute, you can go to a health centre ("vårdcentral"). Call 1177 for information about where to find one. Keep in mind that it might take several hours for symptoms to develop. For example, these may include headaches, nausea, shortness of breath, coughing or irritated airways.
Warning in the event of chemical spills
In the event of chemical spills which threaten life or health, the leader of rescue services will alert those in the affected area via an Important Public Announcement ("Viktigt meddelande till allmänheten"). These are broadcast via Swedish Radio and transmitted as text messages on Swedish public television ("Sveriges Television" or "SVT"). SMS or text messages can be sent to mobile phones in the affected area. Krisinformation.se posts these warnings on this website, and in Swedish on Twitter and Facebook.