Removing Pet Dander and Hair

Question:
Your blog is interesting; very clear and easy to understand. Do you have any advice on reducing pet hair and dander (in addition to vacuuming) in a home where people suffer from allergies?

Response:
Pets allergies can be a significant problem not only for people living with the pets but also for their visitors. Short of finding your pet another home, pet allergies can be best reduced by removing exposures to pet dander, loose skin flakes, hair, urine, and saliva --the main causes of pet allergies. This basically means that you have to get rid of all pet produced allergens (or allergy-causing pet products) -- a difficult and if not impossible task, especially for cats, which have particularly "sticky" dander.

The reason that it is so difficult to get rid of all pet allergens is that pets produce these allergens constantly and that once produced, these allergens (especially from cats) can be carried everywhere. As a result, your house can only be kept clean of pet allergens if you clean your home constantly. The best and most feasible way for you to do so will be to install a whole house air cleaner or several portable air cleaners (see my earlier posts for information on air cleaners). In addition, you will need to clean your furniture and surfaces (especially cloth surfaces) using a vacuum cleaner with HEPA bags. As I discussed in my earlier post on home renovation and dust, HEPA bags in your vacuum cleaner will make sure that any dust picked up by your vacuum cleaner stays in your vacuum cleaner.

These cleaning methods should be accompanied by other ways to minimize your exposures to pet allergens, including frequent hand washing (especially after touching your pets), keeping your pets off the furniture, installing blinds instead of curtains, and keeping your pets outside as much as possible. Also, you should keep pets outside of rooms in which you or the allergic person spends a lot of time, such as bedrooms. You should keep in mind, however, that pet allergens will still get inside these rooms (especially if you have cats), as the pet allergens will be brought into the rooms through your clothes, shoes, bags, and other items that travel room to room. I know that many of these potential solutions are challenging and at least in my house seemingly impossible. But, following these suggestions as much as you can should help to minimize pet allergies.

Portable vs. In-Duct Air Cleaners

Question:
What is the difference between a portable air cleaner and an air cleaner added into my central heating and cooling system? I can’t tell whether central or portable air cleaning systems are better.

Response:
Portable air cleaners are small appliances that typically are placed on the floor of a room in your home and plugged into an electrical outlet. They are designed to clean one room in your home. A whole house or in-duct air cleaner is added to your central air handling system and is installed by an HVAC contractor. Whole house air cleaners clean air inside rooms that are served by the central air handling system.

To use a whole house air cleaner, you will need to have a central forced air handling system. If you do have such a system and you want to clean the air in your whole house, an in-duct air cleaner will likely do a better job than portable air cleaners. This is because the in-duct air cleaners tend to have a much higher Clean Air Delivery Rate or CADR, which tells you how much air the device can clean. For best performance, the CADR should be approximately equal to the square footage of the indoor space that you want to clean. [For more info, see my earlier entry about portable air cleaners.] Also, whatever air cleaner you choose should be labeled as at least 98.98% efficient or HEPA, which means the device performs as a high efficiency particulate air cleaner. A HEPA-grade whole house air cleaner will typically have CADR ratings of about 1200, while the CADR for portable air cleaners is much smaller -- about 250. Theoretically, five portable air cleaners would provide the same performance as one in-duct air cleaner (250 times 5 equals 1250). However, testing has shown that this is not true. In fact, five portable air cleaners together have a CADR of only about 600, since portable air cleaners are not as effective at cleaning air outside their immediate vicinity.

For more detailed information about whole house and portable air cleaners, you may want to check out a report of a study funded by the air cleaner manufacturer TRANE, which compared the performance of several air cleaners, including their own in-duct air cleaning system. Since I know the person who led the study very well (and since I advised in the design of the study), I believe that the data and results are fairly and accurately reported, even though I am usually suspect of studies funded by a group that has something to gain by the results. This report can be found on the internet at www.trane.com/Residential/Downloads/EHE_study.pdf.

Portable Air Cleaners: Things to Consider

Question:
What portable indoor air cleaner should I buy to remove air pollution from inside my home? I want to use the air cleaners to reduce my wife’s suffering from multiple chemical sensitivity.

Response:
If your wife spends most of her time at home in one or two rooms, then placing a suitable portable air cleaner near her in each room should help reduce particle levels - and thus improve your indoor air quality. If she spends time at home in many rooms or your home has an open floor plan, portable air cleaners may not be the best solution. You may want to look at other possible solutions, such as a whole house air cleaning system. You should be aware that air cleaners generally don't remove everything -- most don't remove bad smells or get rid of all potentially harmful gases from the air – be suspicious of such claims.

Portable air cleaners are the most common type of air cleaner. They are small and plug into the wall much like a counter-top kitchen appliance or a portable heater. There are many brands and models of portable air cleaners to chose from. In choosing the best portable air cleaner for you, you should consider the following three factors:

Efficiency. Most portable air cleaners use a filter to remove dust and other particles from air that is moved through the filter by a fan. The efficiency of the filter is the fraction of particles removed by the filter. The best performing portable air cleaners have HEPA-grade efficiency, meaning that they remove at least 99.97% of 0.3 micron particles from the air that passes through them.

Clean Air Delivery Rate. The performance of portable air cleaners is typically determined by its “Clean Air Delivery Rate” or CADR. Conceptually, CADR is the amount of clean air delivered each minute by the air cleaner. In practice, CADR can be calculated from the airflow rate of the fan and the filter efficiency. For example, a portable air cleaner with a flow rate of 200 cubic feet per minute (cfm) and a 50% efficient filter would have a CADR of 100 cfm. CADRs can usually be found on the box of the air cleaner. [The Association of Home Appliance Manufacturers (AHAM) provides more detailed explanation of air cleaners and lists model-specific CADRs at http://www.cadr.org/consumer/certified.html.] Notably, portable air cleaners without fans, such as many ionic type models, do not have a CADR rating because they do not have a fan to deliver air through the filter. As a result, models without fans are generally ineffective (e.g., are a waste of money) because they don't clean enough air to make a difference in your air quality.

Room Size. Portable air cleaners work best inside an enclosed space, for example a bedroom with closed doors and windows. The best air cleaner for your home will have a CADR equal to the square footage of the room that you want to clean. An air cleaner with a substantially larger CADR may be too noisy and create too many drafts. On the other hand, an air cleaner with CADR much smaller than the area of your room will not clean the air fast enough for your room size. In this case, you could purchase several portable air cleaners which together have a large enough CADR to clean the same large room. This solution may be sufficient for your needs, although testing has shown this solution to be relatively inefficient.

On a more personal note, I would stay away from ionic or electronic air cleaners that produce measureable amounts of ozone , a pollutant that has been shown to be harmful to health. Look for test results from companies making ionic or electronic air cleaners to make sure that the air cleaner does not produce measureable amounts of ozone (say over a couple parts per billion or ppb) in your living space. Some ionic or electronic air cleaners will include a scrubber to remove the ozone. I would still be wary of these air cleaners, as it is possible that faulty operation, installation, or maintenance will result in the build up of harmful levels of ozone inside your house. Since there are many available air cleaners that don't produce ozone, I don't see a reason to choose a model that may pollute your air.