I have an extensive backgroung in building and repairing all
sorts of electronic devices. Like millions of others I spend
more time in front of my Desktop than actually breadboarding
circuits, but I still remember most of what I've learned over
the years.

I recently purchased a very high quaility air purifier. I'm
sure many of you have seen these large drum style air purifiers
that use HEPA filters. That's what I've got. I resisted buying
one for years but my allergies have become increasing worse as
I've grown older, so I really had no choice.

Here's the problem. The up and down volume controls, as well as
the power switch on my TV remote instantly shuts the air purifier
down and resets its programmable timing functions to 12:00 AM.
Naturally I ran out and purchased a different remote. A foolish
thing to do, but if there was chance the problem would go away
I was willing to spend the extra bucks. Unfortunately, it didn't
help.

I tried shielding the IR detector in the air purifier display
with a dark red lens. The same kind you see in convertor boxes,
etc. I put up some carboard around the display to see if it
might deflect the IR pulses away from the detector. I discovered
that the lens would practically have to be opaque before it would
stop reacting to the TV remote. I kept increasing the size of
the cardboard deflectors. The cardboard finally did block the
bouncing signals from TV remote. It also completely stopped the
IR pulses from the air purifier's own remote!

Many years ago a defunct electronics hobby magazine published an
article I wrote about a simple on-off IR controller. Right after
the detector module I included a simple integrator consisting
of a resistor and capacitor. This created a short time lag which
blocked the transmission of spurious signals. If this new air
purifier didn't have 5 year warranty I would open the darn thing
up and insert an integrator with a nice long delay.

Each press of a switch on the TV remote is very short. The pulse
would have no effect on the air purifier's detector if the
integrators time interval were two or three times longer than a
typical press on one of those membrane switches.

I tried moving the purifier around the room to no avail. Nothing
seems to help. I'm hoping someone with more expertise than myself
might come up with a suggestion.

Holophote