Using Plans and Specifications 
Editor's note: This article is drawn from chapter 6 of D. Jeff Burton's IAQ and HVAC Workbook, available for sale from AIHA.
My previous Synergist articles have stressed the importance of ventilation in maintaining adequate air quality for employees and building occupants. Since we, as OEHS professionals, are responsible for providing safe and healthy conditions, we must be familiar with ventilation systems, how they are built, their specifications (for example, airflow rates), and how they operate. To that end, reading, understanding, and using a ventilation system’s plans and specifications—commonly referred to as P&S—is always useful.
D. JEFF BURTON, MS, PE, CIH (VS 2012), CSP (VS 2002), is an industrial hygiene engineer with broad experience in ventilation used for emission and exposure control. Send feedback to The Synergist.
VENTILATION TERMS HVAC: Heating, Ventilating, Air Conditioning. OA: Outdoor air—fresh air brought into the HVAC system. RA: Return air—air returned from the occupied space to the HVAC system for conditioning and reuse.  SA: Supply air—air delivered to a space consisting of OA mixed with RA.  CFM: Cubic feet per minute, the airflow rate. Register: A louvered opening at the end or beginning of ductwork.  MERV: Minimum Efficiency Reporting Value, a measure of a filter’s efficiency, ranging from 1 to 20.

ASPECTS OF P&S OEHS programs routinely review P&S for proposed new building and equipment installations. We also review P&S when problems arise in existing facilities and equipment. That allows us to identify deficiencies and potential problems before construction begins, or when something goes wrong in existing facilities. 
The following are the main aspects of P&S.
Complexity. Although P&S can look complicated, just the opposite is true. Yes, they are very detailed and busy, but they are also very simple when broken down to individual components. Drawings and specifications are produced so that everyone can know exactly what is expected. “No detail overlooked” is the aim. Ask for help if you don’t understand them. Currency. If the P&S are for an existing building or system, ask if they are up to date. (P&S that match the current system are sometimes called “the as-builts.”) If they are not up to date, ask about changes. Standards. P&S should follow recognized codes and standards—for example, mechanical codes and ANSI Z9 ventilation standards. When reading P&S, we should check to make sure they are meeting codes and standards. Formats. P&S follow standard forms, symbols, and formats such as those described by the Construction Specifications Institute, which is known as the CSI MasterFormat. Standard formatting makes reading and understanding P&S easier. P&S are broken into sections or divisions: electrical, structural, mechanical, and so on. For ventilation, it is the mechanical P&S that we should concern ourselves with. Coverage. The IAQ-specific information we usually look for in P&S includes:
  • Square footage of the space, ceiling heights, wall and door locations, and related information.
  • Where people are located in the space and the number of people per space or zone.
  • The locations of HVAC equipment such as mechanical rooms, controls, outside air intakes, ducts, and supply air (SA) and replacement air (RA) placements. (See the sidebar for definitions of common ventilation terms.)
  • Types of equipment such as devices for airflow management (dampers, terminal boxes), humidifiers (steam or evaporative), filters (including the Minimum Efficiency Reporting Value or MERV number), and air supply and return registers (locations and controls).
  • Ductwork locations and construction.
  • Types and locations of system control equipment, such as flow monitors, thermostats, and humidistats.
  • SA, RA, and outdoor air (OA) delivery rates; airflow monitoring mechanisms. 
Plans and drawing formats. P&S drawings come in different types, but most can be broken down into the basic elements shown in Figure 1. An isometric drawing provides a three-dimensional view. A plan view shows how the equipment looks from above. An elevation drawing shows detail from the front, back, or side. Dotted lines show interior features that are hidden from view. A section drawing slices through a drawing at the "section line" and turns the cut object to face us. (The drawing in the upper right of Figure 1, labeled Section A-A, is an example of a section drawing.) 
CASE STUDY The following case study illustrates how OEHS professionals can use P&S to address IAQ-related complaints from building occupants. Rod, a university IH, has been asked to investigate complaints of “odors, stale and stagnant air, temperature differences in the space, and allergies” during the winter in a small, one-story, open-area office building that houses about 15 clerical workers and their desks, computers, cabinets, and other common office furniture.  The building was originally built in 1988 and was intended to provide space for typists and clerks. In 1992, the building was converted into a storage warehouse for paper records with no full-time employees. In 2018, with all records now stored electronically, the building was again converted to an open-area office space. Rod reviewed the written reports of IAQ complaints and made a walk-through survey of the building, confirming the complaints with the office staff. He then found the building’s P&S in the Maintenance Department. He asked Terry, the building operations manager, to help him understand them. (See Figure 2 for a simple plan view of the building showing SA and RA registers. North is up.) Rod first asked if the P&S were up to date. Terry indicated yes, they were, and not much had changed since 1988. Rod then asked, “Is the HVAC system operating under the standards and specifications of 1988?” Terry answered in the affirmative, as far as he knew. Studying the P&S, Rod and Terry compiled the following data: 
  • The open-area office had about 1,800 square feet and was intended to house up to 20 employees.
  • The HVAC system was mounted on the roof near the east end of the building. SA and RA ducts were located in a plenum between the office ceiling and the roof.
  • Total SA was designed to be about 1,200 cubic feet per minute (cfm).
  • Fresh OA was set at 7 cfm per person, which met the minimum standard defined in the 1988 version of ASHRAE 62, Ventilation for Acceptable Indoor Air Quality. (For up to 20 people, the total OA would equal 140 cfm.) 
  • SA was provided through ceiling supply registers located near the center of the office space.
  • RA was returned to the HVAC equipment through return registers located in the ceiling near the east end of the building. 
  • An old thermostat was located on the east wall.
  • Air filters in the HVAC system were rough fiber filters, rated at about MERV 3.
Rod then checked the actual HVAC equipment and made some cursory measurements of airflow through the system and in the office space. Informal test results appeared to confirm the information in the P&S; for example, the OA rate was still about 140 cfm and the SA rate was near 1,200 cfm. Rod wrote a report about his findings. He noted that the OA rate was not meeting current standards: airflow in the space was uneven; most of the SA flowed east from the supply registers, leaving the west end of the space cooler (in winter) and with less fresh air; filters would not meet current standards; and so on. He recommended the following actions and changes:
  1. Reformat the existing HVAC system to supply at least 400 cfm OA (20 cfm OA per person x 20 people) to comply with current standards of practice. 
  2. Move the thermostat to the middle of the room on the north side.
  3. Provide ceiling return registers in the west end of the office area so that SA will flow both east and west from the center supply registers.
  4. Equip the system with MERV 11 filters to help those complaining of allergies.
  5. Update P&S for all changes made to the system.

After these changes and updates were made, complaints ceased.
Figure 1. Types of drawings found in P&S.
Figure 2. Simplified plan view of open- area office space showing positions of air registers in the ceiling. North is up.
Resources  AIHA: IAQ and HVAC Workbook, 4th ed. (2017). American Society of Heating, Refrigerating and Air-Conditioning Engineers: Standard 62.1-2016, Ventilation for Acceptable Indoor Air Quality (2016). American Society of Heating, Refrigerating and Air-Conditioning Engineers: Standard 62.2-2016, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings (2016). Construction Specifications Institute. EPA: “Building Codes and Indoor Air Quality” (September 2010). Wikipedia: “MasterFormat.”