Call your CO-Certified contractor at any level below 70 ppm, unless you have symptoms. CO exposure can cause nausea, severe headache, shortness of breath, chest pain, blurred vision, and dizziness. If you experience these symptoms call 911 and leave the house immediately. Above 70ppm, evacuate immediately. If you have symptoms, call 911 from a neighbors house. Call your utility to turn off the equipment until your COCertified contractor can investigate the source of carbon monoxide.