Indoor air pollutants have been ranked among the top five environmental risks to public health. Stagnant indoor environments allow pollutants to build up and stick around in greater amounts than we humans should be breathing in. Thereby, in continuation with the last article where we discussed about basic concept about Indoor Air Quality (IAQ) and various types of indoor air pollutants; this article is focused on strategies to enhance indoor air quality.

Even though the factors that affect quality of indoor environment are numerous, the good news is that most indoor environmental problems can be prevented or corrected. Achieving better IAQ in buildings requires proper application of science and technology. It calls for an optimum combination of proper buildings materials, effective ventilation systems design and indoor pollutant control mechanism. Some broad guidelines for better IAQ are briefly described below.

Materials Selection

Selection and use of low-emitting, non-toxic materials to construct and furnish the buildings is one of the key elements to meet a goal for good air quality. The evaluation process for materials calls for understanding the emission potential of each product under consideration. Several categories are considered in a standard testing procedure, including amount of particulates, total volatile organic compounds (TVOCs), and formaldehydes. Materials and products that are third-party certified for conformance with accepted IAQ standards are the most recommended. Examples of IAQ third-party Certification Programs include certified laboratories.

Whether or not a product is certified by a third party, the designer can receive copies of the Technical Data Sheet and the Material Safety Data Sheet (MSDS) associated with each product from the product manufacturer. These resources provide a bank of information on a product, including hazardous ingredients, toxicological properties, other potential product hazards and safe working procedures. Product or technical data sheets are often the best sources for finding the VOC content of a material, which is key to IAQ considerations. This information is given in grams per liter (g/L) or in pounds per gallon (lbs/G), and most standards list the permissible VOC content in g/L. A hazardous chemical component measured as less than one per cent of the material’s content does not have to be listed on the MSDS; however, if it is an OSHA-identified carcinogen, then limit drops to 0.1 per cent.

General Principles of Materials Selection

 Avoid materials with high emissions rates.
 Eliminate specification of materials that contain known carcinogens and toxins.
 Take special care in selecting materials that will be used in large quantities.
 Check for high VOC levels in materials associated with ‘wet’ processes, including paints and coatings, adhesives, sealants, sealers, caulks, etc.
 Specify materials that can be installed with nails, screws, mechanical fasteners instead of adhesives.
 Specify durable products that are easy to maintain without the use of toxic solvents or cleaners.
 Applications like flooring and furniture often use manufactured or composite wood products, such as plywood, particleboard or chipboard. Use only composite wood products made without urea-formaldehyde resin, which off-gasses formaldehyde at room temperature.
 Avoid the ‘VOC sink effect,’ in which porous materials with large surface areas such as carpets and upholstery, adsorb VOCs and release them over a long period of time, thereby, becoming another VOC source. One way to minimise this problem is to install porous materials only after wet-applied finishes have cured.

Ventilation Systems

Traditional way to improve poor IAQ is to increase ventilation to purge the contaminants. This works well for volatile organic chemicals and bio-effluents like CO2 and odours. But what do you do when the outside air quality is worse than the inside air? In these cases, the pollution is coming indoors from outside, as opposed to the traditional indoor air quality problem of pollution being inside and trying to get it out.

Ventilation systems involve introducing exterior air into an interior space while exhausting stale interior air to the outside. Thereby, mechanical system with adequate ventilation rates and efficient air-filtration is one of the key strategies for better IAQ. In case of a centralised air-conditioning system, this can be done at fresh air units and/or air handling units. Whereas, in case of spaces with unitary air-conditioning systems, air purification units or air purifiers will be the available choice.

Indoor Plants

All plants release oxygen through photosynthesis, but some special species may have built-in air-filtering systems, too. In 1989, NASA discovered that several common houseplants may actually remove carcinogenic chemicals like benzene and formaldehyde from the air especially in enclosed spaces with little air flow. This study has been the basis for newer studies about indoor plants and their air cleaning abilities. While plants have less horsepower than air purifiers, they’re more natural, cost effective, and therapeutic.

Plants are also known to:

• Increase mood and productivity
• Enhance concentration and memory
• Reduce stress and fatigue.

NASA recommends two or three plants in 8 to 10-inch pots for every 100 square feet. Some plants are better at removing certain chemicals than others. Household chemicals come from objects and materials like:
• Carpets
• Glues
• Ovens
• Cleaning solutions
• Synthetic materials such as plastic, fiber, and rubber.

Most benefit is achieved by including a variety of plants in a particular room.

The champion plants in removing benzene are ivy, gerbera daisies, pot mums, peace lily, bamboo palm, and Mother-in-law’s Tongue.

Trichloroethylene (TCE) is largely employed in the metal degreasing and drycleaning industries, printing inks, paints, lacquers, varnishes, and adhesives. The best TCE removers are:

• Peace lily (for TCE from cleaning products)
• Dracaena (TCE from adhesives, ink, dyes, lacquers, paints and varnishes)
• Gerbera daisy (TCE from adhesives)
• Bamboo palm.

During Construction

The indoor air in buildings and homes can be compromised by construction activities even before occupants move into a space. In both residential and commercial sustainable projects, a ‘Construction IAQ Management Plan’ should be prepared by the contractor and approved by the client or designer prior to commencement of the work. IAQ strategies should then be implemented during interior construction works to avoid health issues for workers (during construction phase) and occupants (during occupancy phase).

During Operations

Both workers and management can take steps to help maintain good indoor air quality. For employees, EPA recommends the following:

 Refrain from blocking air vents, as doing so can unbalance your office’s HVAC system and affect the ventilation of neighboring offices.
 Comply with your building’s smoking policy and smoke only in designated areas.
 Clean up spills immediately and report any water leaks to management to avoid the possibility of mold growth.
 Dispose of all garbage promptly in the proper receptacle.

Store food properly. Do not leave food in your desks or on shelves.

Contact building management if you suspect an IAQ problem.

EPAs tips for employers include:

 Maintain a good working relationship with building management regarding IAQ issues.
 Regularly check your building’s HVAC system to ensure it’s in good working order, and coordinate with building management when responsibility for design, operation and maintenance of the ventilation system is shared, EPA states.
 Create a policy that protects nonsmokers from secondhand smoke exposure.
 Refrain from using products that can cause IAQ problems.
 Use pest control products only when necessary, and non-chemical methods if possible.

While above strategies can be a good start, there can be several other more elaborated strategies applicable to different type of buildings or applications. As experienced in such IAQ projects, a thoughtful and integrated design approach is required to be applied in a building design to achieve enhanced IAQ.