Chester LabNet - Offers inorganic analysis of air samples, including source emissions, ambient and indoor air, with filters available for personal use. Lists methods, and customer services available in Tigard, Oregon. ActiveSET.org - Directory of stack monitoring firms in Canada and the USA. Trace Analytics, LLC - Accredited analytical laboratory specializing in the testing and analysis of compressed air and gas used in manufacturing, breathing and medical facilities. Texas Research International, Inc. - TRI Air Testing, an AIHA accredited laboratory, performs compressed air testing, indoor air testing and medical gas testing for fire departments, dive shops, medical facilities, manufacturing plants and the military/government. Air Quality Services - Indiana based firm offering ambient air monitoring services to businesses for compliance with environmental regulations related to air quality. Apex Emission Testing - Supplier of stack and vent emissions testing services throughout Southern Africa. Apart from isokinetic testing, also offers ambient air quality sampling and assessment services to industry.