Zone 2 greater than 2E-4 grams/meter cubed, but less than 2E-3 grams/meter cubed
To put that into perspective a CFM56 with a mass flow of 1000cum/sec will be ingesting between 0.2 and 3.0 g/sec
Or 12 - 180g/min
or 720 - 10,800g/hr
Even though the great majority of that goes through the fan and not the core it won't take long to build up accretions if only a thousandth part of that gets to stick...