In a conventional toilet smells are exhausted by a high level fan,
typically 60m^3/hr run for 10-15mins.
When the toilet is a commode in a bedroom, with irritable bowel
syndrome, the odour issue is more complicated. The commode is mainly
re convenience, there are no major health issues - just eczema foot
bandaging significantly restricts mobility and profile bed keeps it up
and actually damn comfortable for her!
1 - Fit a high level fan on 15min runback timer?
May require compensatory heating since bedrooms tend to be cool. £27
for a decent Xpelair DX100PC fan.
2 - Fit a hydroponic 4" duct fan & duct & activated charcoal filter?
Does not expel room heat, just moves air through a large charcoal drum
filter. Noise is high, but they are powerful for smelly plants so
running time may be short. £75 for a kit.
3 - Fit a fancy 2lb activated charcoal equipped with HEPA air
Does not expel room heat, noise is low so running time is longer.
Limited to 2lb charcoal, expensive filters. £220 for a unit, £70
filters a year.
I never recall the activated charcoal things working that well with
recirculating cooker hoods, either in speed or absolute removal. I
know HEPA filters work for allergies, I picked up a big Honeywell drum
HEPA unit for £49 a decade ago and it eliminated hayfever totally
(replacing it by near complete deafness :-)
A fan extract seems to be a simple cheap solution, and improves
general ventilation in the bedroom. A window is easy to open, but they
are very large and a bit brutal in January.