Occupant health and physical needs are affected by indoor air quality and thermal conditions.

Employees’ physical and task needs can be influenced by indoor air quality (IAQ) and thermal comfort. Unpleasant odours, hot or cool sensations, skin/eye/nose/throat irritation, fatigue, breathlessness, and other symptoms can result from poor IAQ and thermal comfort, making the environment uncomfortable and even unhealthy. Occupants can experience low satisfaction, poorer concentration, and more sickness; a good ventilated environment can allow employees to concentrate on their tasks.

Air quality and thermal conditions also affect employee recognition needs. Ventilation controls, office policies, and good communication allow occupants to determine some environmental conditions so that they are comfortable, meet their individual preferences, and feel valued.

Indoor Air Quality
IAQ is both a health and a comfort issue for occupants. According to ASHRAE Standard 62-2001 acceptable indoor air quality is "air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction." ^[1] Good indoor air quality involves adequate oxygen, low contaminant levels, and the absence of irritating odours.

The Health Effects of Air Contaminants
Contaminant levels can affect comfort or health. All contaminant levels should be kept as low as possible, because the high number of contaminants and long-term, low level exposure can create discomfort and IAQ-related symptoms.

Contaminants can cause a wide range of symptoms from odour annoyance, headaches, and eye/nose/throat irritation to viral and bacterial infections, nausea, and allergies. Contaminants can also be connected to problems like breathlessness, fatigue, drowsiness, difficulty concentrating, and depression. These symptoms can be related to a rises or falls in contaminant levels over time, locations in the room or building, ill health, high humidity, temperature discomfort, or chronic exposure. IAQ-related symptoms generally disappear within minutes or hours of leaving the building, and, as such, are not clinically verifiable; however, they are still uncomfortable and disruptive for employees. The presence of these symptoms may indicate high contaminant levels and should be investigated.

Some contaminants pose a higher threat to occupant comfort and health. For these contaminants, eminent organizations have established guidelines, which are designed to maintain satisfaction and health. The following chart lists the recommendations from two American institutions: the American Society of Heating Refrigerating and Air-Conditioning Engineers ^[2] (ASHRAE) and the National Institute for Occupational Safety and Health (NIOSH).^[3]

Carbon monoxide is one of the most toxic of the possible office air contaminants and should be regulated carefully. It is an inorganic, odourless, colourless gas that is an asphyxiant. In office settings, it usually originates from vehicle exhaust and cigarette smoke. The symptoms of carbon monoxide poisoning are headaches, decreased alertness, flu-like symptoms, nausea, fatigue, rapid breathing, chest pain, confusion, and impaired judgment.

Carbon dioxide is an odourless, colourless inorganic gas. At high levels, it becomes an asphyxiant; however these levels would only ever occur in offices under very extreme circumstances. In offices, there can be enough carbon dioxide to cause drowsiness, and levels should be regulated by ventilation to keep occupants comfortable and alert.

Ozone is another of the most toxic inorganic gases that can occur in offices. Symptoms of ozone exposure include eye, nose, throat, and upper respiratory tract irritation. Ozone can be difficult to regulate because indoor levels are primarily determined by outdoor ozone levels; if ozone is a problem, filters should be used because ventilation strategies may be inappropriate.

Formaldehyde is the Volatile Organic Compound (VOC) most commonly found in offices and is often considered separately from other VOCs. It is a colourless gas that has a strong chemical smell. Formaldehyde can be smelled long before it is dangerous, but the smell itself causes odour annoyance. Formaldehyde exposure symptoms include dry, sore throats, nosebleeds, headaches, fatigue, reduced memory and concentration, nausea, dizziness, breathlessness, and burning or stinging pain in the eyes and mucous membranes.

Sulfur dioxide is a gas generally produced in industrial processes. When inhaled, sulfur dioxide exacerbates asthma, chronic bronchitis, other respiratory tract problems, and cardiovascular problems. When dissolved in water, sulfur dioxide becomes a highly corrosive acid: sulphuric acid. Charcoal filters can help control sulfur dioxide levels if they are a problem.

Nitrogen dioxide is a gas released during many combustion processes. The most common office sources are tobacco smoke and vehicle exhaust. Nitrogen dioxide exposure causes discomfort in the eyes and the respiratory tract, and in larger concentrations it can damage tissue. Charcoal filters are needed to remove nitrogen dioxide from the air.

Particulates vary in size from 0.001 to 1000 microns in diameter. Particles less than 10 microns can be inhaled; however particles of all sizes can cause problems for occupants. Depending on the type of the particle, the particles can cause symptoms ranging from allergy symptoms and skin irritation to lung diseases. Fine filters such as HEPA filters and electrostatic air cleaners can remove the smaller, more dangerous particles from the supply air. Good cleaning and maintenance procedures also play an important role in particle control.

VOCs are gases that can cause a range of symptoms: headaches, eye irritation, dizziness, nausea, acute allergic reactions, and life-threatening diseases. While there are no standards for most VOCs in office environments, many organizations are trying to identify common sources and determine acceptable maximums for the health and comfort of sedentary occupants. The existing industrial VOC standards are too high for office workers and sedentary occupants. The following chart lists some current VOC recommendations for offices ^[4].

In non-industrial environments, there are generally many types of contaminants at low levels. Because of this situation, it is unlikely that any one contaminant will be toxic. It is also unlikely that the source of any problem will be identifiable. Office managers and building operators should collaborate to deal with contaminant sources through isolation, elimination, filtration, and ventilation.

Overall Thermal Comfort
ASHRAE defines thermal comfort as the state of mind that expresses satisfaction with the thermal environment ^[5]. It is a subjective impression based on the occupant’s perception of temperature, humidity, and the effort needed to remain comfortable. In offices, a majority of complaints are related to thermal comfort.

To experience thermal comfort, occupants require comfortable temperatures, satisfactory humidity levels, and the ability to adjust their comfort.

Not everyone is satisfied by the same conditions, during all activities. Occupants need the freedom to satisfy their preferences. People regulate their comfort by changing their clothing, activity levels, posture, or location. They may alter the thermostat setting, open or close a window, or leave the space. Complaining can also be considered a method of regulating thermal comfort; however, it does not immediately improve the occupant’s situation until the problem is acted upon. Office policies allowing occupants to change the environment, their activities, or their clothing can contribute greatly to thermal comfort and to employee satisfaction.

Local Thermal Comfort
Although overall room temperatures may be comfortable, occupants can still experience local discomfort. Temperature differences, either over a room or radiating from a source, can create local discomfort.

Vertical and horizontal temperature differences: In a room, the temperature is not always uniform depending on the arrangement of the room and the supply air diffuser, and the location of heat or cold sources: windows, uninsulated walls, equipment, sunlight, etc. Normally, ceiling air is slightly warmer than floor air because hot air rises. However, if these temperature differences are drastic, occupants can become uncomfortable. Hot ceilings and cool floors, in particular, create local discomfort. Cool floor temperatures can be created by a lack of floor insulation, cool supply air at floor level, or cool space underneath the floor, like a basement or the ground. Raising the room temperature does not always solve the problem: floor insulation or floor heating systems should be considered.

Radiant heat or cold: Radiant temperature difference occurs if there is a heat or cold surface that radiates towards an occupant; this situation effectively creates different thermal conditions on opposite sides of the occupant. These types of problems are normally created by equipment (heat source), poorly insulated windows (cold or heat source), poorly insulated walls (cold source), cold floors, etc.

Draught is one of the most annoying thermal comfort issues. As defined by ASHRAE, draught is “unwanted local cooling of some part of the body by air movement” ^[6]. The air temperature, air speed, and fluctuation of the two determine the extent of the discomfort. At high temperatures, some air movement is desirable and makes occupants feel more comfortable; however, in most office settings, the air is cool and the draught is uncomfortable. Occupants are sensitive to draught on exposed skin, particularly at the head and ankles.

Inappropriate humidity levels also decrease comfort. Humidity creates moisture or dryness sensations on the skin. High relative humidity levels cause skin to feel moist and sticky. They may also create conditions that encourage mould or fungi growth. Relative humidity levels below 25 % can cause feelings of dry skin and irritated mucous membranes ^[7]. Dry conditions also contribute to static electricity, which is potentially damaging to office equipment.

Complaint Handling
Often occupant complaints are the first sign of a problem with the air quality or thermal environment. Responding to complaints is an effective preventative strategy. Prompt attention also satisfies occupant recognition needs and makes them feel valued. It is important to record the complaint and contact the appropriate authority to have the problem solved.

Sometimes the source of a complaint may not be related to the ventilation, but to lighting or acoustic problems, job stress, or ill health. Problems in one area can change occupant perceptions of indoor air quality. It can be very difficult to attribute symptoms directly to ventilation problems, particular contaminants, or poor air quality. All complaints should be investigated.

Good communication between building managers, building operators, and office staff should be maintained so that problems can be diagnosed and solved as quickly as possible. Good communication also maintains good working relationships and prevents disputes and dissatisfaction.

Personal Control
Controls can meet occupant physical and task and recognition needs by allowing them to adjust their own environments in response to personal preferences, without having to call upon building managers or operators. Personal air supply diffusers can be provided in each workstation, either on the desktop, at the floor or ceiling, or built into the modular furniture. These outlets can allow users to adjust the temperature and airflow direction to regulate thermal comfort and draught problems.

Office policies can also give employees control over their environment. Letting occupants to dress comfortably in their offices, permitting open windows, and allowing occupants to adjust the thermostat can be especially significant for thermal comfort.

All occupant controls need to be accessible and easy to use to be effective.

References:
1: American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). (2001). Ventilation for acceptable indoor air quality (ANSI/ASHRAE Stadard 62). Atlanta, GA: ASHRAE. Pg. 3

2: American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). (2001). Ventilation for acceptable indoor air quality (ANSI/ASHRAE Stadard 62). Atlanta, GA: ASHRAE. pg 7 Table 1.

3: National Institute for Occupational Safety and Health (NIOSH). (2000). Annual registry of chemical substances. Washington, DC: NIOSH. Pg.

4: Charles, Kate. COPE Report on VOCs (Available soon)

5: ASHRAE Technical Committees and Task Groups. ASHRAE Handbook: Fundamentals, 2001. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2001. pg. 8.1

6: American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). (1992). Thermal environmental conditions for human occupancy (ANSI/ASHRAE Standard 55). Atlanta, GA: ASHRAE. pg. 3.

7 Nathanson, Tedd. Indoor Air Quality in Office Buildings: A Technical Guide. Health Canada, 1995. pg. 22.