Passport & Visa Information

If you plan to attend the 2024 Air Sensors International Conference being held in Pasadena, California from a country other than the United States, please do not delay in making visa arrangements for your entry if needed. Such arrangements are the responsibility of attendees and participants and may take several months to process through the United States government. Depending on country of origin and length of stay in the United States, you may or may not require a visa to enter the country.


United States regulations require all persons traveling to the U.S. to present a passport or other valid travel document. For more information on travel documents and passports please review the Bureau of Consular Affairs website


Complete information on visa requirements, and if needed, how to apply for a visa to enter the United States can be found on the US Government website.

Many citizens of Canada and of the 38 countries that participate in the Visa Waiver Program (VWP) can travel to the U.S. for up to 90 days without obtaining a visa, as long as they meet certain requirements, which now include an approved authorization through the Electronic System for Travel Authorization (ESTA). ESTA applications may be completed online and submitted at any time prior to travel.

If you are not a citizen of these countries or are not eligible to participate in the VWP, please click here, to find out how to obtain a visa. If you do not have access to the Internet, contact your nearest U.S. Embassy or Consulate for further information.

Remember that having a U.S. visa allows you to travel to a port-of-entry—an airport, for example—but does not guarantee entry into the U.S. Once you arrive in the U.S., an official will need to interview you and verify your paperwork in order to grant you admittance to the country.

YOU SHOULD SECURE YOUR VISA INTERVIEW AT LEAST 90 DAYS PRIOR TO YOUR SCHEDULED DEPARTURE TO THE U.S. This will allow the necessary time for processing of both your application packet, and the visa. For more information about Safe Travels, International and ESS, International, please visit their website.

Conference Invitation Letter

Most countries will require visa applicants to provide supplementary information explaining the purpose of their travel. In this regard, providing a letter of invitation to ASIC 2024 may be useful. If needed, please download the invitation letter to apply for a Visa to attend ASIC 2024

If you need a customized letter, please generate it yourself and e-mail it to our AQRC Events Staff at, for review and signature. Please allow for one week processing at UC Davis.