Clean Air Refugee Assistance Act of 2018 This bill authorizes the President, in carrying out the Transitional Sheltering Assistance Program of the Federal Emergency Management Agency (FEMA), to provide transitional shelter assistance to individuals living in an area where the air quality index is determined to be unhealthy for not less than three consecutive days as a result of a wildfire declared by the President to be a major disaster or declared to be a major disaster by the governor of the state in which the individuals are located.