Heating, Ventilation and Air Conditioning (HVAC)

Temperature - Relative Humidity - air movement - ventilation that adequately removes odors and contaminants expected in a space and reintroduces 'clean' air of a quality and quantity that provides adequate oxygen levels and minimizes irritants or unhealthy contaminants in occupied spaces  ----These are the basic functions of HVAC systems for occupied spaces.  But there is so much more to be considered than just comfort. A properly designed and installed HVAC system includes concerns for Health. The industry doesn't like to use that word, because it is like opening a can of worms. The number of variables involved is pretty much astronomical! Every individual is different, so 'health' becomes highly personal- not where building and system designers want to go - when any of millions of people could be passing through THIS building they are working on now. But, building codes and standards are all dealing with not only 'safety', but general health of building occupants. So there it is- HEALTH. 

What does that mean? Do no harm is the basic idea. 

So- what may be comfortable, may not necessarily be healthy (or doing no harm). Sometimes people choose unhealthy things because they like (comfort) them. An example is adding a lot of 'pretty' odors to our spaces rather than removing the causes of the 'not-pretty' odors, or properly ventilating the space to remove the 'not-pretty' odors. Example: the mustiness of an older carpet can be disguised by use of air fresheners and odor absorbers. But the mold that is the cause of the mustiness is still present. Now the occupants are exposed not only to the mold, but also the chemicals in the air 'fresheners'. 

Industrial Hygiene deals with occupant health and safety specifically in industrial type environments, however application of the concepts and principles to all occupied spaces provides a good basis for delivering and maintaining work and living spaces that have GOOD indoor air quality for the use and activities of the space. Risk analysis (an industrial hygiene concept) should be used to guide design,  investigation, remediation and operational recommendations and procedures. HVAC designers should use the principles of evaluating potential and expected air quality risks in order to properly handle these risks through the design and operation of the HVAC system, as well as dealing with the comfort issues. 

PROACTIVE: HVAC systems should be designed for the specifics of the building, not just the space- as the space is not independent of the building assemblies and dynamics. Additionally, the building is located in a specific geographical area with climatic, geographical and environmental characteristics. Going back to the basics to evaluate the conditions needed in the indoor space for either occupants or processes and understanding the owner's priorities including indoor conditions, maintenance staff requirements, operational costs, first costs and redundancy needs is imperative. Then, experience must be applied to apply basic evaluation methods, codes and application realities to get the best overall solution for the specifics of the building and occupants / uses - always remembering that if the basic calculations are based on improper information, the results will misdirect the entire design. 

REACTIVE: When an existing building is not performing correctly, the best place to start is with the building itself. Information can be gained in a site visit that may never become evident in a multitude of documents. Some basic measurements, observations and simple testing give the 'symptoms' of what is happening and where (a critical aspect of understanding the dynamics involved in every building). Basic observation techniques including feel, smell, visual and sound clues are critical observations that help interpret measurements and testing results. This information provides guidance and direction to the path of discovery needed to fully diagnose the issues - what calculations might be needed, what additional testing or diagnostics, what documents to look for, etc. Each situation is different, but all have their own story to tell - and a bit of detective work is needed that includes listening to those already involved in using the building and caring for it. 

Mechanical Engineers have a broad spectrum of knowledge that encompasses the physics of heat, moisture, materials behavior, sound and vibrations, structural element / stress behavior, water and gas flow, corrosion, chemical interactions with materials, electrical current effects, change of energy forms, (mechanical/electrical/heat/light/sound/vibration/rotational. etc.). Application of these physical principles is the backbone to controlling our built environments, but incorporation of industrial hygiene concepts creates the link to human physiological needs for both survival and thriving in their environment. As engineers gain experience working with the built environment- they should be gaining awareness and appreciation for the emotional and psychological influences that their work has on the occupants of spaces and their satisfaction and productivity. From temperature /  humidity / comfort to noise, smells and visual influences - our work spaces and living spaces dramatically affect our ability to be creative, productive and interact with civility and compassion.