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Testing – Sterilization & Killing Microbes

As manufacturers of antimicrobial products for heating ventilating and air conditioning systems, there is a type of call we get often. It goes something like this: (Caller) ‘Does your xyz product kill (name of specific bacteria or fungus)?’ (BBJ representative) ‘I can’t tell you for sure. We have not tested our product against that organism.’

The call may be from a building owner. More often it is from a contractor who has been called on to correct an indoor air problem. They are considering an antimicrobial product as part of their solution. They are asking about a specific organism because someone has suggested that particular organism may be causing the problem and must be killed for the problem to go away. The most important role for antimicrobial products is preventing problems in the first place not hunting out and killing growth once a problem is present. But, that is another article. Today we are going to look at the tests that identify an organism to be killed, why we do them, and if the results are meaningful or helpful.

This subject was the topic at a Forum held at the recent ASHRAE meeting in San Francisco. It was interesting to me that the opinions expressed by the ‘experts’ who participated in the forum were very much like those I have held for years. Some of the observations expressed at the meeting included:

  • There are few if any solid guidelines as to what level of microbial growth is a problem so it is difficult to interpret test results.
  • A ‘clean’ report may cause an owner to not continue the search for a problem and lead to continued exposure of occupants to contamination.
  • False readings can be given if samples are not gathered correctly.
  • It is difficult to analyze the data even from those tests that are conducted correctly.
  • A sample gathered in one part of the building or at one particular time of day could be suspect by itself. Only numerous samples gathered at various times of the day and on different days provide meaningful data.
  • Correct sampling is very expensive. Generally, the money is better spent on prevention or remediation.
  • Test results could be used by the other side in a lawsuit yet is unlikely to help in defense of an IAQ related matter.

Generally, the attendees concluded that if mold or other growth is visible, it should be removed and steps taken to prevent its regrowth. Testing is of little value yet quite expensive if done correctly. Money is better spent on proper maintenance.

Why Do We Test?

In spite of the above opinions, a lot of testing is done. Why? The answer is that it seems natural and logical. When we want to see if a HVAC system is producing the correct temperatures, thermometers give us immediate accurate readings and we have clear guidelines about how to evaluate those readings. Electrical testers and pressure gauges give us important information about a system. Therefore, our training and experience prepares us to look for test results that will help us to correct a problem. It only stands to reason that tests that tell us the number and type of organisms present in a building should be of value. The problem is that there is nothing to do with the data when we have it. Also, microbiological testing is not as straightforward or dependably accurate as other measures we are used to using.

Are Individual Organisms Important?

When we go to the doctor with a sore throat, a sample will generally be taken and sent off to a laboratory to find out what kind of organism is present. If we get a massive infection, the doctor will normally do a culture of the bacteria causing the infection. These tests are done because antibiotics are manufactured that are highly specific for a certain organism. That way the germ that is causing the disease or condition can be targeted without exposing the body to drugs that might kill the beneficial organisms that live on the skin and in the digestive tract.

There is no parallel in the building environment. Antimicrobial products that are manufactured for the control of organisms in building environments and HVAC systems are designed to be ‘broad spectrum’. That is, they are meant to kill the widest variety of organisms possible without being overly toxic to humans and animals. This is because there are no beneficial organisms in building environments. Even those that are normally thought of as friendly like those that help create compost out of dead plant matter can cause damage to building structures and furnishings and give off gasses that are irritating and potentially harmful. Therefore, we want to control all growth not just selected organisms. As manufacturers, we assure effectiveness of our products by testing against some of the organisms that are thought of as being resistant. If we are successful in controlling those, we assume that our products will control all organisms. There are tens of thousands of different organisms. It would be neither possible nor affordable to test all.

What Do We Do?

The old saying that prevention is the best medicine clearly holds true here. The best way to avoid problems with microbial growth is to concentrate on a well-planned and carried out preventative maintenance program. Control moisture and repair leaks at once. Keep the facility and especially the HVAC system clean. Properly utilize bacterial control products where growth is likely such as in air handlers. Routinely inspect and immediately remove any growth observed with products designed for that use and used according to manufacturer directions.

Dated: March 3, 1998

Bob Baker is a member of ASHRAE and Chairman and CEO of BBJ Environmental Solutions, Inc., a manufacturing company specializing in providing clean air through environmentally responsible products, such as BBJ MicroBiocideâ„¢, BBJ Micro Coil Cleanâ„¢, BioSoft Spray Disinfectant/Cleanerâ„¢, and Fresh Ductâ„¢, as well as The Indoor Air First Aid Kitâ„¢. For additional information, Mr. Baker can be reached at (800) 889-2251 or through the company web site at http://www.bbjenviro.com