Frequently Asked Questions
No lines have appeared at all, why?
This usually means that the blue liquid has not been allowed to settle fully in the Sample Extraction Buffer bottle so that neat fuel has been added to the test well. As the test fails-safe, no lines will be seen. However, the test cannot be reused and a new foil pack must be opened.
Are the control lines supposed to be brighter than the test lines?
Yes, the control line shows that the kit has operated properly and should be very distinct. The test line is a response to the level of contamination in the fuel and is usually less bright.
But the test line is very faint, does that mean that it is positive?
No, if you can see a test line, even a faint one, that has a definite colour (i.e. is not a shadow) then the test is negative. This is due to the fact that the line does start to fade when the contamination level is near to the action levels, and then disappears when it exceeds the limit. So, if you can see a line then the level is below the cut-off point, so the test is negative.
Do I need to incubate the sample or the test paddle?
No, unlike other traditional growth methods used by our competitors, no incubation is needed for the Fuelstat™ resinae test.
Do I need to use sterile equipment to take the sample?
No, because the Fuelstat™ resinae test only detects H. resinae that has been growing in fuel, it does not matter what other organisms get into the sample. Using clean equipment is good practice, though.
Are there any restrictions on disposal of the test?
No, the paddle and the sample bottle can be disposed of with normal refuse. Any fuel used in the sample extraction bottle should be disposed of with the remainder of the sample taken from the aircraft tank.
Why have you set time limits for reading the test results?
The test should be read between 10 and 30 minutes after placing the four drops into the sample wells. The 10 minute limit is required because that is the time that the test needs to operate fully. We then guarantee the results for a further 20 minutes. In fact, nine times out of ten the result displayed will stay visible for a couple of days. However, in certain conditions of heat and humidity, and under certain bright light conditions, the picture may fade away. That is why we ask you to read it in that 20 minute period.
Other kits say that all organisms should be counted and not just H. resinae, is this true?
H. resinae is by far the most serious organism in aviation fuel in aircraft and short-term storage. In other fuels and longer-term reserve stores, where organisms have longer to develop, a much wider range of organisms come into play. This is why Fuelstat™ resinae has been specifically designed for aviation systems. Other organisms may be present but will not be causing the same amount of damage as H. resinae. Organisms never occur in isolation and where significant numbers are present, we find that H. resinae will be there as the most significant organism.
Can Fuelstat™ resinae be used to show whether biocide treatment has been successful?
Fuelstat™ resinae measures a change in the fungus that only occurs when it is grown in aviation fuel. If the fuel is successfully treated with a biocide, this will begin to diminish straight after the treatment. To ensure that the treatment has been successful, a further test is required within 7 days of the treatment, but after at least 5 flights. If levels have not reduced to negligible then the biocide has not been totally successful. A further biocide treatment is then required, using a full fuel load and the maximum soak time. H. resinae is more resistant to biocides than bacteria so other kits that only monitor bacterial growth within the shorter incubation periods will not indicate whether the H. resinae has been dealt with. H. resinae requires an absolute minimum of 4 days to begin to grow.
We use a dip slide. They are very cheap and are just as good, why should we pay extra for your test?
Dip slides are not designed for use with fuels. They will give incorrect, non-reproducible, counts and, of most concern, they will usually under-represent the problem. The manufacturers themselves do not recommend them for this purpose and are concerned with their use in fuel.
What do the Low and High levels mean in terms of colony forming units (CFU)?
Fuelstat™ resinae does not measure CFUs and the results cannot be directly correlated. The measurement of CFU for filamentous fungi is very inaccurate. CFUs have come to be accepted only because nothing better was available. The problem arises because of their structure; a mass of intertwined fibres, bearing long chains of spores. Each CFU may originate from a single spore, a clump of spores or a piece of fragmented hyphae (the “rooting” system). Any correlation to the actual biomass is, therefore, tentative. Fuelstat™ resinae overcomes this problem by measuring a change in all parts of the fungus which occurs when it grows on fuel. This also correlates directly with the fungal biomass present. This changed material is also released into the fuel and the water phase where the amount can be measured in micrograms (µg).
The tests are set to the following levels:
Negligible: up to 150 µg/l
Low Positive: 150 – 750 µg/l
High Positive: over 750 µg/l
Negligible: up to 33 µg/ml
Low Positive: 33 – 166 µg/ml
High Positive: over 166 µg/ml
These levels have been established after laboratory calibration studies, and comparative studies on over 400 field samples.
What happens if the device gets wet?
If the device is soaked either by water or fuel it will fail-safe. I.E. the control lines will not appear.