Washington State Motor Vehicle Emission Inspection Stations 18610 NE 67th Ct, Redmond, WA98052 Emission checks are required every two years for those vehicles in the emission check areas (the website will tell you…More if you are in a check area). The best days to test at the Redmond Station are during the middle two weeks of a month, and on Mondays. The best times to test are afternoons and mid-mornings. Avoid the last week and the last testing day of the month. The emissions check website offers helpful tips such as driving your vehicle on the freeway for 15 miles before testing, turning off all accessories once in line and refraining from shutting off your engine while in line. Also, avoid bringing pets and passengers.