AQS User Support is provided through the EPA Call Center, which is operated under contract to the EPA.
The toll free number is 1-866-411-4EPA - (4372). TDD: 1-866-489-4900, International callers: 1-703-679-1070
Their hours of operation are 6:00am - 9:00pm E.T. (Monday - Friday, excluding Federal holidays).  You may also contact the Call Center via email   (EPACALLCENTER@epa.gov) or fax (703-674-1008).

The Exchange Network Services Center (ENSC) is EPA's electronic reporting site. ENSC support is available toll-free between the hours of 8:00 am and 6:00 pm (EST) at 888-890-1995 - choose option 2 for Node Helpdesk Supportor via email at nodehelpdesk@epacdx.net.

Contact a National or Regional EPA representative or a State, Local, or Tribal Agency representative http://www.epa.gov/airquality/airdata/ad_contacts.html

• aqs regional contacts (PDF)(1 pg, 51 K)