is a requirement when preparing an EIS, but is optional in an EA. The response to these  comments will depend in large part on the types of comments made combined with the  discretion and judgment of the responder. However, some comments may  request, or  even necessitate, an expanded air quality assessment for a proper response.  By applying the information acquired and/or developed through the course of these preliminary  steps, the air quality analyst should have ample justification for deciding  what type of an  air  quality assessment is warranted.  Consultation with state or local air quality agencies,  EPA  regional offices, and FAA (for projects and actions requiring FAA involvement)  may still be  necessary however.  For ease in further determining what type of air quality assessment is appropriate for projects or actions,  Figure 4-3  ( Air Quality Assessment Decision Flow Diagram ) provides a  simplified decision tree based upon the information provided and discussed above. As shown,  the fundamental decision pathways and terminal nodes are based upon such factors as (i) whether  or not the project/action will cause a reasonably foreseeable increase in emissions, (ii) whether it  is located in a nonattainment/maintenance area, and (iii)  whether additional or other specific  analyses have been required during the agency/public scoping and coordination process.  Figure 4-3. Air Quality Assessment Decision Flow Diagram  22$_{ }$ Aviation Emissions and Air Quality Handbook 