4.  Air Quality Assessment Process  4.1. The Air Quality Assessment Process  In the most fundamental terms, the air quality assessment process  –  from conducting an  assessment to documenting the results - can be broken down into four steps. As shown in  Figure  4-1  ( Air Quality Assessment Process ) and expanded upon in this section, this process entails the  following: Step 1: Determine the Need for the Assessment  – The purpose  of this initial step is to help determine the overall need  and  scope for an air quality assessment. It is intended to be broadly  applied to all FAA projects based on the project definition as  known during the early planning and development s tages. As  discussed in  Section 4.1.1  (Step 1: Determine the Need for an  Air Quality Assessment),  this step takes into consideration such  factors as the FAA’s role in the project  and the potential  significance of the anticipated air quality impacts as well as the  “scoping” process (detailed in  Section 9.1 ,  Scoping Process )  which is used to identify the most pertinent air quality issues  related to a project/action.  Step 2: Select the Assessment Methodology  – The purpose of  this second step is to determine the type(s) of  air quality  analyses that are appropriate for the particular project/action.  As discussed in  Section 4.1.2  (Step 2: Select the Assessment  Methodology),  the range of analyses comprises  a qualitative  discussion, emissions inventories of various types and sources  of  emissions  (e.g.,  operational,  construction,  etc.) ,  and  dispersion modeling macroscale and “hot -spot”). In  addition, this step can involve agency coordination with the  development and application of an “Air Quality Assessment  Protocol”. The main purpose of the protocol is to document the scope, establish  a  methodology, and resolve any areas of uncertainty regarding the assessment prior to its  undertaking (detailed in  Section 9.2 ,  Air Quality Assessment Protocol).  Step 3: Conduct the Assessment  – Once the need and methodology of the air quality  assessment has been evaluated and selected, the purpose of this step is to prepare  or  conduct the air quality assessment. As discussed in  Section 4.1.3  (Step 3: Conduct the  Assessment),  this work may involve selecting the analysis years, identifying the emission  18$_{ }$ As discussed in  Section 1  ( Introduction and Background ), the primary aim of this  Handbook  is  to provide guidance in preparing air quality assessments for FAA -supported projects and/or  actions. Importantly, the overall premise is that some type of assessment or consideration of air  quality is always necessary under NEPA or the CAA - whether it be qualitative or quantitative.  Focusing on this principal objective, this section is designed to help  Handbook  users determine  what type of air quality assessment is appropriate and to formulate an approach to preparing the  assessment.  Aviation Emissions and Air Quality Handbook  Figure 4-1. Air Quality Assessment Process  Step 1. Determine the Need for the  Assessment  Step 2. Select the  Assessment  Methodology  Step 3. Conduct the Assessment  Step 4. Coordination/ Review and  Documentation of  Results 