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Invalid
Exponent
(n)
Threshold
The air flow exponent, n, is used to describe the airflow regime through the gaps and holes in
the building fabric. Values must range between 0.5 and 1.0. An n value approaching 0.5
signifies turbulent flow, representing high flow through large apertures. An n value
approaching 1.0 will indicate a more laminar flow, characteristic of more air tight structures or
those with much smaller gaps and holes.
A test would fail on this criteria if the n exponent is outside of the 0.5 to 1.0 range. A value
that is below 0.5 would typically be caused by a building having a series of very large
openings. This could be as basic as there being an open window or chimney but it could also
simply mean that the building is just too leaky overall and outside of the operating range of
the Pulse equipment in hand.
It is very rare for an n exponent of more than 1.0 to be recorded but if it is, we advise
assessing the achieved pressure range, perhaps repositioning the equipment e.g. ensuring the
controller is not in the turbulent flow from the air receiver nozzle, then retesting.
Invalid
Steps
As with the test as a whole, individual steps have their own pass and fail criteria, however one
step failing doesn't mean that other steps have also failed. If a test presents an 'Invalid steps'
fail message, then this means that the final result calculation included at least one step which
failed. The reasons for why steps have failed will be displayed on the 'Parameters' tab when
viewing a test in Pulse Online.
7.9
After testing
When all testing is complete, we advise draining the air receiver prior to transport. Draining is best achieved by
draining the air receiver using the dedicated function on the control system (see section 8.3).
Switch-off the unit, unplug all wires and store.
Pulse is now ready for transport.
