Gradual Background Increase

East coast Vancouver Island, Duncan British Columbia
There has been a marked increase over the past three months. The average for October was 28 CPM, for November 29 CPM, and for December 2015 is pushing 33 CPM. The past two days, the 24 hour average was 35 CPM.
I thought the jump from 33 CPM to 35 CPM might have been caused by closing the window because it was freezing outside. Last night, Dec 23, midnight, I opened the window and recorded the same level.
Weather has been alternating cold, wet, heavy rain, with seasonal storm fronts similar to records from last year.
Last December, 2014, the background was 10 CPM lower, but unfortunately, those records were with the pancake detector enclosed in a nylon camera case and mounted vertically.


Readings are taken with an Aware Electronics RM-80 pancake (LND7313) and AW-RADW software. This detector is on the window sill, facing up, usually in direct draft from outside. Air is constantly being drawn in by the apartment building ventilation system.
This is a corner, ground floor apartment, concrete under carpet. Heat is from circulating hot water baseboard radiator. Window sill is 1 metre above ground level.
Radon from the foundation is present, but at low levels, probably because it is drawn out by the building vent system.
I will be giving the detector mesh an alcohol wash and blowing the mica window clean today. At midnight, December 23, I will be putting the detector back in the camera case, then mounting it vertically in the same location.

As an update to this post on increased readings, they seem to have levelled out at an average of 32 CPM over the past three months. Highest one minute average has been 34 CPM, whether the window is open or not.

I've been comparing readings with those from Atomic Dave in California, who is using the same type of pancake detector. His detector is on his desk, uncovered, mica window facing up. A couple months back, I moved my RM-80 detector from the window sill to the computer desk and our readings have been averaging about the same.

Brian, VA7BDG