For MicrobMonitor®2

What is the MicrobMonitor®2 test?
  • A small glass bottle containing a thixotropic nutritive gel formulated specifically to grow microbes associated with fuel and oil spoilage.
  • Supplied in boxes of five and fifty tests with sterile devices for measuring and dispensing fuel, oil and water samples.
  • A simple, novel and safe way of assessing the numbers of colony forming units (CFU), the standard unit for measuring numbers of microbes.
What is the test used for?

Identifying and quantifying microbial contamination in petroleum products in storage, distribution and use including:

  • Aviation, automotive, power & marine fuel
  • Bio fuel, heavy fuel and crude oil
  • Lubricants and hydraulic oil
  • Metal working fluids and straight cutting oils
  • Associated water with any of the above

It is also a sensitive test for detecting microbes in water and any other fluid sample.

What is the HS code of the MicrobMonitor2 test?

The Harmonized Commodity Description and Coding System generally referred to as “Harmonized System” or simply “HS” is a multipurpose international product nomenclature developed by the World Customs Organization (WCO).

MicrobMonitor®2 is classified as: Prepared culture media for the development or maintenance of micro-organisms  HS: for export and HS for import.

Why test for microbes in fuel?

Microbial contamination has caused aircraft to abort take off, ships to be taken out of service and power generator bearings to fail. Contamination can, if detected early, be treated and severe operational problems can be avoided.

Routine condition monitoring as part of a good housekeeping regime can significantly improve asset utilisation and reduce operational risks.

Microbial contamination in fuels can cause:

  • Filter plugging, blocking of fuel and oil lines and injectors causing excessive wear and failure.
  • Corrosion of tanks, bearings and other systems
  • Increased water content causing fuels to become hazy and degrade
Who can use the test?

ANYONE – full instructions are supplied and no special skills or equipment are needed.

Can I use the MicrobMonitor2® test for all types of fuel?

Yes. The recommended volume to test may be different though. MicrobMonitor®2 can also be used to test lubes.

How often should I test?

Start with frequent testing (every month for example) and adjust testing intervals according to operational experience and the perceived risk.

Is the MicrobMonitor2® test the only test kit I need?

It is for aircraft tanks as these are well aerated (aerobic), but fuel storage tanks are often partly stagnant, and corrosive ‘anaerobic’ Sulphate Reducing Bacteria can grow. The Sig Sulphide test will enable you to detect SRB.

Is the test reliable?

MicrobMonitor®2 was developed originally for use in the aviation industry for testing jet fuel and is recommended by IATA and listed in the Aircraft Maintenance Manuals of Boeing, Airbus and other major aircraft OEMs. Major airlines have been using the test for many years.

MicrobMonitor®2 has been independently validated in an inter-laboratory study conducted for the Energy Institute and enables testing in accordance with IP Standard Method IP 613 Determination of the viable aerobic microbial content of fuels and associated water – Thixotropic Gel Culture Method.  The test also gives results comparable with laboratory standard test methods IP 385 and ASTM 6974-03.
The test is used by the military and is a codified NATO stock item (Stock No. 6640-99-834-3573)

Why use MicrobMonitor2®?
  • Works with any petroleum product and associated water
  • Approved by major OEMs and oil companies and adopted widely
  • Quick and easy to use, more economic than laboratory tests
  • Uses the reliable and trusted colony forming unit (CFU) technology
  • No specialist skills or equipment required
  • Results are comparable with IP 385 and ASTM D-6974-03
  • Detects low level contamination for an early warning of potential problems
  • Indicates the severity of an infection not just the presence of microbes as with “go, no-go” tests
  • Unaffected by biocides, DIEGME or additives so can validate the efficacy of the treatment
  • Only detects live microbes and mould spores, other tests give positive results for hours or even days after microbes have been killed by a biocide treatment
  • Oil and water phases can be tested
  • Detects active Hormoconis resinae and other moulds, yeasts and bacteria
  • Detects mould spores which some other tests cannot
What about support?

We provide full technical support to all of our customers, regardless of the product or service they are using. Product support via e-mail and phone is completely free of charge to all of our clients, and something we are proud to provide.

What's the easiest way to break up the gel?

It is important to break up the gel in the MicrobMonitor®2 test and shake thoroughly (30 seconds recommended) to disperse the sample in the gel. Inadequate shaking can result in lumpy gel and can result in patchy growth which can make test results more difficult to read and interpret.

Tap the bottle sharply several times (in the palm of your hand) to break up the gel before you shake it. Some users tap the bottle several times on a large rubber bung. Other users warm the tests to about 30°C (86°F) before use; this makes the gels easier to shake. We now supply MicrobMonitor® Bumpers for those who need to shake lots of tests.

When I use the test a pink/peach colour develops in all of the gel. Is this microbial growth?

Possibly not – The stability of fuels and lubes, particularly those formulated with bio-ingredients, is often improved by the suppliers by adding anti-oxidants. These can react chemically with one of the ingredients of the MicrobMonitor®2 test, resulting in a pink/peach background colour. This usually occurs within 24 hours and does not interfere with the growth of microbes transferred from the sample. Their growth produces deep red colonies in the gel which can easily be seen despite the pink background. To reduce the effect you can test smaller volumes of sample, for example 0.1 ml of bio-diesel instead of 0.25 ml. Then use the 0.1 ml section of the interpretative chart.

I sometimes see red patches or streaks in the test. How do I interpret this?


Some bacteria are very motile and they can swim in the test gel to form large purple or red patches or streaks. The patches often have uneven colour intensity. Usually the problem only occurs when testing water samples or fuel samples containing suspended free water.


• Look at the test after 1 or 2 days, before the patch has spread out; count the colonies marking them with a felt pen. If when observed again (e.g. at 4 days), a spreading patch is present, this should be ignored and only new normal colonies counted and added to the total count.
• If it was not possible to observe the test before the patch spread, it is often possible to see through the patch and distinguish and count normal colonies as usual. The patch tends to have a lighter colour intensity than normal colonies and is not clearly demarcated. Each patch should be counted as one colony and added to the total count of normal colonies. If it is difficult to determine where a patch begins and ends, record a count of “1” colony for the patch or streak and add this to the total count of normal colonies.
• If it is not possible to distinguish and count normal colonies through the patch, count only an area of the gel which is not affected and multiply the count by an appropriate factor for the final result (e.g. count half of the gel area and multiply by 2).
• If using the interpretation chart to estimate the total number of colonies, try to ignore the patch and estimate only on the number of normal colonies; if necessary estimate the intensity of colonies based on an area of gel which is unaffected by the patch.
• If none of the above are possible, it may be necessary to repeat the test taking the avoidance precautions described below. You may also send a photograph of any unusual results to and we will do our best to interpret the result for you.


To help you to avoid this problem:
• If testing fuel, allow any water to settle to the bottom of the sample before taking out the fuel for test. We recommend standardising the procedure for testing fuel system samples which contain both fuel and water. Inverting the sample 3 times and then allow it to stand for a few minutes (ideally 2 minutes per cm height of fuel in the sample) so that any water settles. Fuel for test (0.5 ml for aviation fuel or 0.25 ml for other fuel types) should then be taken from half way down the fuel phase, avoiding transfer of visible interfacial particulate, water droplets or emulsion. The water phase or interface can be tested separately if required (0.01ml recommended)
• If you are testing water, you can reduce the chances of getting spreading bacteria and improve the ability to discern individual colonies by testing only 0.01 ml volumes of water using the dispenser provided.
• Use an incubator to keep the temperature constant and reduce condensation on the gel.
• Shake the test properly after adding the sample. Streaky or patchy growth in the test is more difficult to interpret if the gel is not properly shaken and the gel remains lumpy. Always ensure the gel is properly broken up and then shaken with sample for 30 seconds.

Are the limit values for different levels of microbial contamination regulatory or standardised?

There are no microbiological standards in any fuel specification and the limit values suggested can be changed according to the local perceived risk and local operating experience. Large oil companies and major fuel users often have their own in-house limit values.

What Pack Sizes are available?

MicrobMonitor2® is available in packs of 5 tests or in a bulk pack of 50 tests.  The normal packs include all that is needed to conduct the test including sterile syringes and loop dispensers for measuring sample into the test. For users who have their own sterile measuring devices, a bulk pack is also available which does not include syringes or loop dispensers. Such accessories  can also be purchased separately as required.

If I use a biocide in my fuel, will the MicrobMonitor2® test detect survivors?

Yes, unlike some other tests, MicrobMonitor®2 can be used immediately after biocide treatment to check that the treatment has worked (you will still need to allow for a soak time of 24 hours before testing).

I have found ‘moderate’ or ‘heavy’ microbial contamination according to the IATA ‘Guidance Material’ limit values. When I enter the tank I find little evidence of microbial growth. Are the limit values wrong or am I interpreting the results wrongly?

The ‘moderate’ and ‘heavy’ contamination limits as defined by IATA and repeated in OEM’s manuals, are set at levels which enable corrective treatment with a biocide or cleaning + biocide, before there is an operational problem. They do not necessarily mean that the fuel is unfit for use at that time.

When I test both water and fuel phases from an aircraft or fuel storage tank I sometimes find that the fuel is heavily contaminated but the water is clean. How do I interpret this?

This probably means that that the fuel uplifted or imported is heavily contaminated and the growth is not taking place in your tank.

When I test both water and fuel phases from an aircraft or fuel storage tank I sometimes find that the water is heavily contaminated but the fuel is clean. How do I interpret this?

This probably means that that dirty sea water, wash water or environmental water has entered the tank. Drain it off as soon as possible before the microbes adapt to grow in your tank.

Can I store MicrobMonitor2® in the refrigerator?

Yes. If you refrigerate the product from point of receipt (store between 2-8°C in the dark) and have purchased it either directly from ECHA or from an Authorised Distributor, then the shelf life can be extended by up to 10 months. Specific expiry dates for different storage conditions are printed on the batch label of MicrobMonitor2 test kits.

Can I store MicrobMonitor2® in the freezer?

MicrobMonitor®2 may be frozen for short periods e.g. during transport. However we do not recommend long term frozen storage as the properties of the test will change after several weeks.

How do I dispose of MicrobMonitor2® tests after use?

Tests showing any positive results contain microorganisms and should be handled carefully. Avoid touching the inside of the bottle or cap. Dispose of used tests showing microbial growth by incinceration, or by disinfection followed by disposal. Wash your hands and work surface after disposal with antibacterial soap.

Disinfection of used tests can be accomplished by careful addition to each test bottle of two of the “Aqua Tabs” provided with the kits (where available). Recap the bottle and shake vigorously for 30 seconds then leave for 24 hours. Alternatively used kits can be sterilized by immersion open in a solution of strong disinfectant overnight.

After sterilization, bottles should be disposed of in accordance with local waste disposal regulations.

What is the maximum temperature I can test or incubate at?

MicrobMonitor®2 tests will become increasingly more fluid at temperatures above 40°C.  Therefore incubation above this temperature is not recommended as the developing microbial colonies are not likely to remain as discrete during growth.