4 FM quick reads on IAQ
1. ASHRAE Clarifies 62.1 in 2013 Edition
ASHRAE 62.1, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings. The 2013 version, published in October, consolidates the 2010 standard with its 10 published addenda.
In addition to creating a consolidated standard, the 2013 edition has a few changes that were made to resolve inconsistencies and improve clarity, says ASHRAE. Seven of these clarifications are called out as particularly significant by ASHRAE.
First, the ventilation effectiveness of underfloor air distribution systems that meet certain conditions has been increased and is described in Table 6-2, Zone Air Distribution Effectiveness.
Requirements for the quality of water used in humidification systems have been clarified, as well as requirements for building level pressurization. "Exfiltration" has been defined as part of this clarification.
Exhaust rates are now described by the standard via performance and prescriptive methods. "This approach differs from the Indoor Air Quality Procedure, the existing performance-based method for setting supply ventilation rates, in that monitoring of the concentrations of contaminants of concern is required and provides the basis for control of exhaust flow rates," says ASHRAE.
Refrigerated warehouses have been added to the space types in Table 6-1. In the same table, ventilation rate changes have been made for sports-related spaces to allow for demand-controlled ventilation.
Wetted cooling coils now require MERV 8-rated filtration to reduce the chances that particulate accumulation on the coils will lead to biological or other contamination.
And last among the significant changes called out by ASHRAE to the 2013 edition, toilet exhaust air that is cleaned to Class 1 may be recirculated.
Learn more about ASHRAE 62.1: here.
2. Indoor Air Quality Depends on Outside Air Quality Too
IAQ is not just about indoor air quality. In fact, in order to effectively tackle any IAQ issues at a facility, the outdoor air needs to be evaluated as well. For example, is the quality of the outdoor air worse than the inside air? Answering that question can help narrow down sources of contaminants.
So what do you do if the answer is yes and the outside air is contributing to the IAQ problem? First, check the air filters and air dampers on air-supply intakes and clean or replace as necessary.
Maintaining adequate indoor air volume is important to good IAQ, as well as maintaining adequate airflow. To increase airflow, clean the air ducts to reduce particulates, which reduce air volume and are also a source of contaminants. Cleaning the ducts by scrubbing and vacuuming can also remove hidden mold.
Maintaining indoor air quality is so important, ASHRAE is giving away free downloads of its Indoor Air Quality Guide: Best Practices for Design, Construction and Commissioning. The guide describes 40 IAQ strategies related to moisture management, ventilation, filtration and air cleaning and source control, says ASHRAE. It also highlights how design and construction teams can work together to ensure good IAQ strategies are incorporated from initial design through project completion.
Download a free copy of the guide here.
3. Common Sources of Indoor Air Contaminants
Indoor air quality can be negatively affected by airborne contaminants and excess moisture. There are some usual suspects when it comes time to investigate a potential source of harm to indoor air quality. These include:
Air-supply intakes. These can receive an inadequate air volume, are favorite roosting places for birds, and have the potential to introduce contaminated outdoor air.
Sub-roof or below-grade areas. These areas are subject to moist still air, which promotes mold growth. Crawl spaces where water can puddle unnoticed are a breeding ground for mold, pests and allergens that can cause respiratory illness.
Chemical storage areas. Cleaning chemicals, paints and other materials can evaporate and release toxic vapors and volatile organic compounds.
HVAC ducts. Water in ductwork from humidifiers in the winter and condensate in the summer can grow mold. Any time there is high temperature with no air circulation, mold can grow rapidly. Plus, mold can stick on substances that adhere to duct walls, loosen, then enter the air supply.
Another common culprit that's less in your face than mold growth is poor airflow. Diagnosing this problem will require using an air-balance multimeter, which measures individual air velocity, temperature, and pressure. A flow-hood kit saves time by taking multiple air-velocity readings simultaneously and converting them into average airflow rates.
Other tools can be used to provide a more refined analysis of the air to indentify specific particulates or gasses. These include:
- thermal imagers, which detect moisture from roof leaks or piping leaks inside walls, often hidden from view. Wet surfaces are colder than dry areas. The imager detects this temperature differential through building materials
- a hot wire detector, which uses thermal conductivity to measure concentrations of inorganic gases
- a flame ionization detector, which measures concentrations of aliphatic and aromatic hydrocarbons
- an electron capture detector, which detects chlorinated hydrocarbons
- a flame photometric detector, which measures concentrations of sulfur and phosphorus compounds
- a mass selective detector, which measures the volume of IAQ pollutants and can identify unknown chemicals.
4. Data To Measure IAQ Is Complex Proposition
Today's tip is to understand that measuring IAQ is more complicated than a metric such as energy use. Measuring indoor air quality means amalgamating several different metrics to give a holistic IAQ picture.
"There is not just one measurement that can assess the dynamic relationship between the presence of air contaminants and the ventilation to effectively dilute and remove them," says David Bearg, president of Life Energy Associates. "Instead, assessing the healthfulness of an indoor environment is more a matter of measuring key parameters" such as effective ventilation rates, contaminant levels, absolute humidity, and even occupant satisfaction.
"The most important thing is measuring and maintaining airflow rates and exhaust," says John McFarland, director of operations, Working Buildings, Inc. Luckily, air flow is also the easiest IAQ-related metric to measure and benchmark, says McFarland, who is also the vice chair of the ASHRAE 62.1 committee.
ASHRAE 62.1 is generally thought of as a design standard, but facility managers can use its recommended ventilation rates toward IAQ. Determine the cubic feet per minute (CFM) of airflow per person, then use 62.1 to determine if the current airflow rates meet the minimum requirements for the space occupancy, especially if space functions have changed.
Also, a high percentage of completed preventive maintenance bodes well for good IAQ. It means you're regularly checking filters, examining dampers to make sure they're opening and closing properly, and making sure drain pans aren't full of water. Essentially, you're continuously commissioning your systems to make sure they're behaving as they should.
ASHRAE 62.1 also provides a standard for relative humidity (maximum of 65 percent in the 2007 edition), which is another part of the IAQ whole. "Extremes of moisture, either too dry or too humid, can adversely impact IAQ," Bearg says. If the air is too wet, mold can form. But air that is too dry (especially in the winter), makes occupants uncomfortable, says Bearg. So measuring the dew point temperature and humidity, and benchmarking that data, is one of the more important, yet overlooked, parts of getting a holistic IAQ view.
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