So basically no one really knows the answer to this very simple question.
Here's a bit more I've been able to find, non of it from HP.com or any HP resource
# Acknowledgements:
# the JetDirect code is taken from check_hpjd.c by Ethan Galstad
#
# The idea for the plugin (as well as some code) were taken from Jim
# Trocki's pinter alert script in his "mon" utility, found at
# http://www.kernel.org/software/mon
# hrPrinterStatus = .1.3.6.1.2.1.25.3.5.1;
# hrPrinterDetectedErrorState = .1.3.6.1.2.1.25.3.5.1.2
# hrPrinterStatus OBJECT-TYPE
# SYNTAX INTEGER {
# other(1),
# unknown(2),
# idle(3),
# printing(4),
# warmup(5)
# }
#
# hrPrinterDetectedErrorState OBJECT-TYPE
# SYNTAX OCTET STRING
# MAX-ACCESS read-only
# STATUS current
# DESCRIPTION
# "This object represents any error conditions detected
# by the printer. The error conditions are encoded as
# bits in an octet string, with the following
# definitions:
#
# Condition Bit #
#
# lowPaper 0
#
# noPaper 1
# lowToner 2
# noToner 3
# doorOpen 4
# jammed 5
# offline 6
# serviceRequested 7
# inputTrayMissing 8
# outputTrayMissing 9
# markerSupplyMissing 10
# outputNearFull 11
# outputFull 12
# inputTrayEmpty 13
# overduePreventMaint 14