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## 4. Air Quality Assessment Process 

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. 

## 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: 

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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 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 

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 

