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Sampling For Legionella

Legionella Sampling Locations

Sampling is the single most important activity for every project. The purpose of sampling is to identify the goals of the project, to answer specific questions, or to develop a hypothesis to test. While it is normal for clients to be upset when they encounter a suspected case or an outbreak, avoid taking random samples without understanding how the data will be used and who could ultimately see the results. Here are some key questions to consider that will help you focus your sampling efforts:

1. What are the appropriate test methods and the level of detail needed for your project? (See test codes)

2. Where do you need to sample? Are there particular types of equipment or devices that need to be sampled?

3. When do you need to sample? Consider there may be times to take cooling tower samples in the summer and early fall to account

for worst case scenarios rather than taking strictly periodic samples.

4. How many samples do you need to take?

It is important to take as many samples as necessary to obtain sufficient data to answer your questions. Every sampling location should provide data to answer a question, however avoid taking more samples than necessary. Understand that one sampling point or one sampling event will not constitute a representative number of samples and will not pass a legal challenge. The purpose of sampling will vary according to different project goals so adjust your sampling strategies accordingly. Use the “Where to Look” and “Sample Locations” sections to help focus your activities.

If you represent a Veterans Administration Medical Center, understand the required test codes and sampling locations before doing any sampling. Review the VHA Directive dated August 2014 which can be found at http://www.va.gov/vhapublications/ViewPublication.asp?pub_ID=3033

 

 

Cooling Tower Sampling Locations Sample Quarterly

  • Tower Makeup

  • Tower Sump away from makeup* (water and swab)

  • Inlet to Heat Exchanger

  • Distribution Pack

  • Outlet from Heat Exchanger

  • Tower Pack* (water and swab)

 

Potable Water Sampling Locations Sample Semi-Annually

  • City Water Main Entry Point

  • Storage Tanks

  • Hot Water Heater Drain Point*

  • Hot Water Return

  • Last Point on Cold Water/First Point on Hot Water

  • Last Point on Hot Water*/First Point on Cold Water

  • 10% of Selected Outlets (water and swab)

 

* Test Routinely. Test all locations to establish a baseline. Test all locations during an outbreak.

 

 

Sampling Instructions - Legionella

1. Personal safety and precautions should be observed during sampling. Avoid breathing aerosols that may be contaminated with Legionella bacteria. Avoid generating aerosols or water mists during sampling of the water system. Wear a respirator equipped with an N95 respirator, a HEPA cartridge, goggles, and sterile nitrile gloves.

 

2. Prepare or obtain sterile, screw-capped plastic bottles for sampling. Sodium thiosulfate is routinely added to the bottle as a preservative and

halogen (chlorine or bromine)-neutralizing agent.

 

Recommeded Sample Size

 

 

 

 

3. For drinking or potable water, such as water fountains, faucets, and shower heads, collect two samples if possible. Collect the “pre-flush or first draw” sample by draining the first 1000 mL of water from the faucets or flush drains into a bottle. Allow the water to run for approximately 60 seconds and collect the second draw of 1000 mL of water. Leave a one-inch space on top of the water sample. The second sample is also called “post-flush or second draw” sample. Take cold water samples from drinking water fountains and areas that have dead legs. Also take ice samples, allowing them to melt to reach a 1000 ml sample.

 

4. When sampling faucet aerators and showerheads, remove the aerators asceptically. Take swabs of the inside the faucet and shower heads as far as you can reach with the swab. Swirl the swab on the inside of the pipe three times. Your swabbing procedure should be consistent between sampling locations. When sampling cooling towers, whirlpool spas or fountains, look for areas of biofilm and take a swab sample of the biofilm. We will provide sterile swabs for this purpose.

 

5. For non-drinking or non-potable samples from such sources as cooling towers, chillers, condensate pans, surface water in reservoirs, sprinklers, hot tubs, water walls etc., collect 250 mL water from the bottom or side of the vessel or reservoir. If taking a cooling tower sample, also consider taking a sample in the pack column. Leave a one inch space on top of the sample. Record any biocide used in water treatment when collecting non-drinking water. If sampling whirlpool spas, consider taking a swab sample of any biofilm as well as a sample of the sand filter.

 

6. Label sample number on the bottle and record on the sample data sheet. Use a distinctive number for each sample. Complete all sample information on a sample data sheet for your own record. Send a copy with the samples to the laboratory.

 

7. Tightly cap the bottles. Make sure that water does not leak during shipping and transporting. Taping of bottle around the cap and neck with electric vinyl tape is recommended. Place taped bottles in a clean plastic bag. Place the samples in insulated boxes with freezer packs to protect specimens from extreme temperature fluctuations in the summer months. NEVER USE ICE OR DRY ICE. Stuff the box with foam chips to cushion, and seal the box securely for shipping. Send samples by overnight express carrier. Schedule sampling between Monday and Friday so that samples can be delivered to the laboratory no later than Saturday. (Consider holidays)

Contact EMSL for the shipping address to your nearest CDC ELITE lab. Phone: 800-220-3675, Fax: 856-786-0262 Email: info@emsl.com

EMSL provides FREE sterile bottles and swabs for Legionella sampling (shipping cost to/from EMSL is not included).

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