Furnace filter doesn't filter?
 

Due to allergy I installed a filter cabinet and a merv 12 4-inch filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

Furnace filter doesn't filter?
 

On Jan 1, 11:06*am, "bob" wrote:
Due to allergy I installed a filter cabinet and a merv 12 *4-inch filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

Possibly dirt that is already in the heating ducts from
before you put the MERV filter in the system?

Furnace filter doesn't filter?
 

On Sun, 1 Jan 2012 08:06:54 -0800, "bob" wrote:

Due to allergy I installed a filter cabinet and a merv 12 4-inch filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

*Some* dust is normal. Places it comes from and where you might want
to check. . . Did you clean or replace the ductwork when you
installed the expensive filter. [I'm guessing that a 'merv 12 4-inch'
filter is expensive-- I don't know anyhting about them] I'd replace
it myself if you're up to the task. Buy a good respirator before
you begin. You won't believe how much crap accumulates in a decade
or two.

Did you at least check all the ductwork for points of infiltration?
The air gets filtered at the furnace. if there is a pinhole in a
duct it will suck dirt out of whatever cavity it happens to be in.
that's why some folks put filters on the registers.

Jim

Furnace filter doesn't filter?
 

"bob" wrote in message
...
Due to allergy I installed a filter cabinet and a merv 12 4-inch filter
in my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of
the filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

When did you last have your ducts cleaned out ?

You might want to have a closer look at those dust particles under
magnification to have a better idea of their source.

Furnace filter doesn't filter?
 

On Jan 1, 11:06 am, "bob" wrote:
Due to allergy I installed a filter cabinet and a merv 12 4-inch filter
in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of
the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

Possibly dirt that is already in the heating ducts from
before you put the MERV filter in the system?

I forgot to mention I had the ducts cleaned (vacuumed) by the same company
who installed the filter cabinet, which is 3 months ago. They commented the
ducts were very clean already.

The ducts have also been sealed 2 or 3 years ago, and although it is not
100% sealed, the contractor performed a blower door test and said it was
acceptably sealed. The reason I say it is not 100% sealed is because during
the summer, I can smell a faint crawlspace odor coming out of the register
when I'm in the bathroom with the ventilation fan on.

The furnace is about 5 years old.

The 4 inch filter is filtrete brand and cost $30 or so at hardware store.

I will set up a carbon monoxide alarm next to the register just in case.

Are there "serious" air filter for floor registers with merv ratings like
the furnace filters? I see foam-like filter that fits inside the floor
register, but they have no ratings.

Furnace filter doesn't filter?
 

On 1/1/2012 3:06 PM, bob wrote:
On Jan 1, 11:06 am, "bob" wrote:
Due to allergy I installed a filter cabinet and a merv 12 4-inch
filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side
of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

Possibly dirt that is already in the heating ducts from
before you put the MERV filter in the system?

I forgot to mention I had the ducts cleaned (vacuumed) by the same
company who installed the filter cabinet, which is 3 months ago. They
commented the ducts were very clean already.

The ducts have also been sealed 2 or 3 years ago, and although it is not
100% sealed, the contractor performed a blower door test and said it was
acceptably sealed. The reason I say it is not 100% sealed is because
during the summer, I can smell a faint crawlspace odor coming out of the
register when I'm in the bathroom with the ventilation fan on.

The furnace is about 5 years old.

The 4 inch filter is filtrete brand and cost $30 or so at hardware store.

I will set up a carbon monoxide alarm next to the register just in case.

Are there "serious" air filter for floor registers with merv ratings
like the furnace filters? I see foam-like filter that fits inside the
floor register, but they have no ratings.
Help us a little. What does your furnace use for fuel?

Filters usually don't fit tightly in the holder. Did you somehow seal up
around the edges of the filter?

Do you have little critters chewing into the heating vents, or the cold
air return ducts? Perhaps you are smelling them.

Get some "man sized" cleneex and wrap one or two of these under a floor
register. After a week, remove and examine for dust or whatever. Should
be clean if your filter is doing it's job. They are for collecting
evidence, not for regular air filtering.

Paul

Furnace filter doesn't filter?
 

On Jan 1, 1:59*pm, "
wrote:
On Jan 1, 1:35*pm, Evan wrote:



On Jan 1, 11:06*am, "bob" wrote:

Due to allergy I installed a filter cabinet and a merv 12 *4-inch filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

It is the dirt built up in your duct work from before you installed
the
filtration system...

You should have your duct work cleaned, pressure tested and properly
sealed at each connection point and then insulated...

Less dirt in your air with the filter, none can get sucked in at the
joints in the duct work

The portion of the system AFTER the
filter he just installed has positive pressue. *Nothing is
being sucked into it. *On the other hand, the vacuum in
your empty skull, I;m not so sure about

Evan, clueless as usual

Too bad with the reduced ozone layer in the polar regions you
Canadians are exposed to more extra terrestrial radiation...

I assure you mr canadian that crap builds up in ductwork
under positive pressure, with the right amount of moisture
things like to grow too...

And you clearly aren't aware that positively pressurized
duct work creates suction and aspirates when the fans
cycle off if they are not well sealed...

But the OP has replied with more info since...

~~ Evan

Furnace filter doesn't filter?
 

MERV stands for Minimum Efficincy Reporting Value. It's a scale from 1 to
16. A MERV of 12 is currently popular with the heating and AC industry for
filters. It should do a pretty good job of stopping particles above 1 micron
in size. Smaller particles will be less well impeded. Your dirt may be
smaller particles.
Why the focus on dirt? How's the allergy doing? That's the important
thing, not dirt. Are you allergic to things that are bigger than 1 micron?

Dave M.

Furnace filter doesn't filter?
 

On Jan 1, 10:05*pm, Evan wrote:
On Jan 1, 1:59*pm, "
wrote:





On Jan 1, 1:35*pm, Evan wrote:

On Jan 1, 11:06*am, "bob" wrote:

Due to allergy I installed a filter cabinet and a merv 12 *4-inch filter in
my furnace. I thought I'd be getting very clean air.

To verify, I cover two floor registers with furnace filters. After a few
weeks these filters turned dark grey and can be seen from either side of the
filter. I flipped it over and there is no dust accumulation.

Is this normal? Where do the dark fine particles come from?

It is the dirt built up in your duct work from before you installed
the
filtration system...

You should have your duct work cleaned, pressure tested and properly
sealed at each connection point and then insulated...

Less dirt in your air with the filter, none can get sucked in at the
joints in the duct work

The portion of the system AFTER the
filter he just installed has positive pressue. *Nothing is
being sucked into it. *On the other hand, the vacuum in
your empty skull, I;m not so sure about

Evan, clueless as usual

Too bad with the reduced ozone layer in the polar regions you
Canadians are exposed to more extra terrestrial radiation...

Who dragged Canadians into this? I'm not
Canadian, you;re just confused as usual.




I assure you mr canadian that crap builds up in ductwork
under positive pressure, with the right amount of moisture
things like to grow too...



Show us how dirt gets in with positive pressure. Enough
dirt that it's showing up at the registers.



And you clearly aren't aware that positively pressurized
duct work creates suction and aspirates when the fans
cycle off if they are not well sealed...

Show us how dirt gets in with positive pressure. Enough
dirt that it's showing up at the registers.





But the OP has replied with more info since...


And you're the guy who told us not too long ago that
nitrogen had to be recovered from an AC system and
not released into the atmosphere. And how you NEVER,
EVER want to cut and re-glue a PVC exhaust pipe
because everyone is gonna die and that requires
special skills. Meanwhile every idiot around is installing
dryers, for example.

What a fool.

You mentioned that the filters were black color. What type of furnace do you have? It could be possible smoke from the furnace if it's a pellet or wood burning furnace. Or even with a gas furnace, there could be a residue like grease that is burning.