HVAC system

Ventilation and HVAC systems can be used as points of penetration or as delivery mechanisms for chemicals, including gases. All parts of these systems should be located behind fences or out of reach and secured. 

Any communication systems used should be tamperproof to the extent possible. Backup systems and secondary backup systems help ensure continuity of operations during an emergency. Discuss communications with outside emergency responders to help them meet their needs during an adverse event. Utilize all communication systems in day-to-day activities to maximize their effectiveness, ensure systems will operate in times of emergency, and familiarize employees with their use. 

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I oise Transmission Reduction in HVACSystems. One common use of sound-absorbing treatment is to reduce noise transmission in heating, ventilating, and air-conditioning (HVAC) systems (6). The treatments ate used to reduce the transmission of fan noise and air turbulence noise through ducts into occupied spaces. Noise transmission reduction in duct systems is described in terms of insertion loss, the difference in sound power level or sound pressure level measured at a given location before and after installation of the treatment or sound attenuation, the reduction in sound power between two locations affected by a sound source. The units ate decibels. 

DOD/USAF chlordane assessments NASA HVAC system maintenance... 

HVAC the HVAC system is not able to control existing air contaminants and ensure thermal comfort (temperature and humidity conditions that are comfortable for most occupants). 

Indoor air contaminants can originate within the building or be drawn in from outdoors. If contaminant sources are not controlled, problems can arise, even if the HVAC system is properly designed and well-maintained. Sources can be from outside the building from operating equipment, from human activities, and other or miscellaneous sources. Sources outside a building include contaminated outdoor air, emissions from nearby sources, soil gas, or moisture or standing water. 

Commissioning reports Was the building properly commissioned when it was first constructed, including testing and balancing of the HVAC system ... 

Remodeled areas Has the HVAC system layout been changed to accommodate new walls, rearranged partitions, or similar architectural modifications ... 

The walkthrough should focus on uneven temperatures, persistent odors, drafts, sensations of stuffiness. You may find that occupants are attempting to compensate for an HVAC system that doesn t meet their needs. Look for propped-open corridor doors, blocked or taped-up diffusers, popped-up ceiling tiles, people using individual fans/heaters or wearing heavier (or lighter) clothing than normal. 

Check for underventilation caused by obstructed vents, faulty dampers or other HVAC system malfunctions, or from problems within the occupied space. Furniture, papers, or other materials can interfere with air movement around thermostats or block airflow from wall or floor-mounted registers. If office cubicles are used, a small space (i.e., two to four inches) between the bottom of the partitions and the floor may improve air circulation. 

Confirm that the HVAC system maintains appropriate pressure relationships to isolate and contain odors and contaminants in mixed use buildings and around special use areas. Examples of special use areas include attached parking garages, loading docks, print shops, smoking lounges, janitorial closets, storage areas, and kitchens. 

Check the outdoor air intakes to see whether they are located near contaminant sources (e.g., plumbing vents, exhaust outlets, dumpsters, loading docks, or other locations where vehicles idle). See if the space containing the HVAC system is clean and dry. Examples of problems include cleaning or other maintenance supplies... 

HVAC inspections Be thorough in conducting these inspections. Items such as small exhaust fans may operate independently from the rest of the HVAC system and are often ignored during inspections. As equipment is added, removed, or replaced, document any changes in function, capacity, or operating schedule for future reference. It may also be helpful to store equipment manuals and records of equipment operation and maintenance in the same location as records of occupant complaints for easy comparison if lAQ problems arise. 

The elements of a PM plan include periodic inspection, cleaning, and service as warranted, adjustment and calibration of control system components, maintenance equipment and replacement parts that are of good quality and properly selected for the intended function. Critical HVAC system components that require PM in order to maintain comfort and deliver adequate ventilation air include a outdoor air intake opening, damper controls, air filters, drip pans, cooling and heating coils, fan belts, humidification equipment and controls, distribution systems, exhaust fans. 

These sensors can be programmed to record data and to control multiple elements of the HVAC system. 

An initial walkthrough of the problem area provides information about all four of the basic factors influencing indoor air quality (occupants, HVAC system, pollutant pathways, and contaminant sources). The initial walkthrough may provide enough... 

If the hypothesis or model does not seem to be a good predictor of what is happening in the building, you probably need to collect more information about the occupants, HVAC system, pollutant pathways, or contaminant sources. Under some circumstances, detailed or sophisticated measurements of pollutant concentrations or ventilation quantities may be required. Outside assistance may be needed if repeated efforts fail to produce a successful hypothesis or if the information required calls for instruments and procedures that are not available in-house. Analysis of the information collected during the LAQ investigation could produce any of the following results ... 

Identify key individuals needed for access and information A person familiar with the HVAC systems in the building should be available to assist the investigator at any time during the onsite phase. Individuals who have complained or who are in charge of potential sources (e.g., housekeeping, non- HVAC equipment) should be aware that their information is important and should be contacted for appointments or telephone interviews if they will not be available during the onsite visit. 

An evaluation of the HVAC system may include limited measurements of temperature, humidity, air flow, as well as smoke tube observations. Complex investigations may require more extensive or sophisticated measurements of the same variables (e.g., repeated COj measurements taken at the same location under different operating conditions, continuous temperature and relative humidity measurements recorded with a data logger). 

Particulate filtration removes suspended liquid or solid materials whose size, shape, and mass allow them to remain airborne at the air velocity conditions present. Filters are available in a range of efficiencies, with higher efficiency indicating removal of a greater proportion of particles and of smaller particles. Moving to medium efficiency pleated filters is advisable to improve lAQ and increase protection for equipment. However, the higher the efficiency of the filter, the more it will increase the pressure drop within the air distribution system and reduce total airflow (unless other adjustments are made to compensate). It is important to select an appropriate filter for the specific application and to make sure that the HVAC system will continue to perform as designed. Filters are rated by different standards which measure different aspects of performance. 

The series of standards presented in this paper provides a useful package for assessment and design of HVAC systems and protective equipment to be used in moderate, cold, and hot environments. The standards may be used to estimate the optimal combination of environmental thermal factors that will provide comfortable or tolerable healthy working conditions. The standards may also be used to establish optimal work/rest schedules for environments where the working time must be limited owdng to strain on the human body. Several of these standards are being adopted as national standards in several countries. 

Air-handling units equipped with heat recovery and sophisticated control of the key parameters of HVAC systems, such as temperature, airflow rate, and pressure difference... 

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