Fluke CO-220, 975, 922 Service Guide

Carbon monoxide:

A mechanic’s approach

Application Note

It’s not always technical maid ser­vice. Sometimes HVAC professionals
are rewarded with a mystery and
given the opportunity to put our
technical detective skills to work.
How accurately we solve combustion
related mysteries is directly related
to our fundamental understanding
of the science and technologies in
effect, our choice of tools and test
equipment, our previous experi­ences, and even our imagination.

The answers lie beyond
the obvious

Carbon monoxide consumer
awareness is still on the
increase. More and more
consumers are installing CO
detectors in their homes and
workplaces. This is good. It
offers occupants a level of safety
they did not have previously,
and offers the expert (you) an
opportunity for in-depth site
analysis.

So how does it usually unfold?
An occupant calls the fire
department after a CO alarm.
The firemen may not see an
obvious source of the CO, so they
recommend having the furnace
(or boiler) checked by a heat­ing contractor: the combustion
expert. It’s your job to find the
source of the CO under current
conditions, or to try to duplicate
variable conditions under which
CO could be produced. This is a
tall order, requiring a process of
elimination of possible malfunc­tions and a keen awareness
of variables, such as building
depressurization and gasses (air
and vent products), that could
behave unexpectedly.

While you’re driving to the
jobsite, turn off the radio and
think about the abundant pos­sibilities. Think of the structure
in its entirety as a system.
Combustion appliances are only
a part of the integrated whole.
What else is competing for or
interfering with combustion air,
fuel supply, vent function? How
can contaminants such as chlo­rides, sulfides, VOC’s, dust, and
dirt affect component integrity
and operation?

Think about some of the
questionable creative engineer­ing you’ve seen from end users
trying to save on energy costs.
Think about all of the different
fossil fuel appliances and prod­ucts, wood fireplaces and stoves
that may be in play: some fixed,
some portable, some that drive
away. Think abo ut what could
be external to the structure
that could produce combustion
products and be drawn into the
occupied space: idling school
buses or trucks, standby gen­erators in exercise mode, poorly
placed or improperly installed
vent terminations.

The list of possibilities is
seemingly endless, and more
often than not, it’s two or more
processes gone wrong. One
process may have been operat­ing on the edge of acceptability
since day one, and a second
process changes enough to
throw the first process over the
edge. Every job is different and
valuable lessons can be learned
from each. Be observant and
allow your mind to explore the
possible system failure modes
and their interacting effects.

Exterior survey

When you arrive at the job­site, observe the exterior of the
system (the building and its
immediate surroundings). Before
entering the building, turn on
your environmental air meter
(such as Fluke 975) and give it
time to warm up and zero out­doors. This will give you time
for a walk-around.

F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w . f l u k e . c o m / l i b r a r y

Notice chimneys, vertical
vents, sidewall vents, air intakes
and exhausts, exhausts that
could become intakes (such as
drier vents that stick open from
lint build-up), building penetra­tions proximity to doors and
windows, and meter locations.
Look underneath decks and
porches, at the garage location,
inside corners for vents, and
notice shrubberies and trees,
prevailing wind direction and
possible effects, and foundation
type (slab, crawlspace, base­ment). Look in window wells
and crawlspace access wells,
and just generally notice things.

Later, as you focus on indi­vidual components such as the
furnace or boiler, water heater,
venting and ventilation, you
will return to the outdoors to
pay more attention to the details
and interactions of functions.
You might be surprised by how
a seemingly unrelated outdoor
feature can affect the indoor
function of a process.

Questions to ask

Once inside the structure, consider yourself as a combination of
police detective and crime scene investigator.

Here are some questions to ask:

What kind of CO alarm sounded?

•

When did the alarm sound?

•

Was it a standard CO detector

•

designed according to UL 2034 that
specifies that alarm must sound
within 1 to 4 hours at 70 ppm CO, or
do they have a low level alarm model
that sounds after 5 minutes when CO
reaches 15 ppm to 34 ppm?

Can you retrieve the maximum CO

•

level retained in the alarm memory?

What CO level did the firemen find?

•

What other comments did the fire-

•

men have besides suggesting to call
the heating contractor?

Did the alarm sound during early

•

morning hours when all were asleep
indicating possible ventilation and
venting problems?

Did any of the occupants exhibit any

•

physical symptoms?

Did it sound after everyone was

•

awake indicating a possible occu­pant created condition from space
heaters or automobile warm up in an
attached garage?

Did it sound on Sunday afternoon

•

when friends or relatives came for
dinner?

Did they burn the roast, burn the

•

biscuits, or burn the food in the pan
on a burner they forgot about?

Is there an exhaust fan in the kitchen

•

over the stove and is it used?

Was an outdoor cooking grill used

•

and at what location?

What about gasoline powered tools

•

and equipment?

Is smoking allowed indoors?

•

Did it sound shortly after everyone

•

retired for the night and was the
fireplace used on that night?

Check more than just CO

Before you leave the outdoors,
record the outdoor ambient CO
so you can compare it to indoor
levels. Outdoor levels could be
as low as 380 ppm CO

or less

2

in rural and seacoast loca­tions, or above 500 ppm CO
congested urban locations. Then,
as you start your indoor survey,
record CO
humidity on your air meter.

LEED-EB IEQ2

ppm, CO ppm and

2

(1)

Credit 1 CO2
concentrations can range from
less than 1,000 ppm CO
2,000 ppm CO

depending on

2

2

per person ventilation require­ments and Met (metabolic) rate
activity levels.

(2)

Elevated CO2
(from respiration) can be an
indicator of a poorly ventilated
structure, but unvented (spill­ing) combustion products will
elevate CO

and humidity levels

2

in the occupied space as well.
Increased CO

levels in kitchens

2

may be due to decomposing
organic material (garbage).

CO

and water (vapor) are

2

produced in the complete com­bustion of fossil fuels, and CO

2

in

2

to over

and water (vapor) are produced
from incomplete combustion. A
furnace, boiler or water heater
typically produce 80,000 ppm
to 30,000 ppm (8 % to 13 %)
CO

depending on fuel type,

2

and about a gallon of water per
100,000 Btu input. If a category
I vent is spilling combus­tion products, the first change
an occupant may notice is
increased condensation on win­dows due to elevated humidity
that hadn’t occurred previously.

The first rule of fire

Fire must be safely confined
and controlled while maintain­ing correct fuel supply, oxygen
supply, and ignition temperature.
When we build a fire indoors,
we must know that the combus­tion products will vent to the
outdoors. Appliances designed
to operate over extended periods
of time like a furnace, boiler or
water heater must be vented
directly to the outdoors. Products
with limited operating times
such as residential stoves, ovens

and space heaters are usually
expected to have products of
combustion in quantities low
enough to be vented by normal
building ventilation, which
may be relying entirely on the
natural infiltration of air through
structural leaks. As oxygen is
consumed and vent products
exit the building, fresh air from
outdoors must be continuously
supplied or disaster will follow.

Combustion analysis

Warm up and zero your com-

•

bustion analyzer outdoors.

Combustion products must be

•

sampled undiluted before any
draft hoods, barometric draft
dampers, or any dilution air
injection. (Some high effi­ciency direct vent boilers may
draw air from the air intake
into the combustion air blower
prior to the exhaust pipe.)

Sample the O2 and CO on

•

startup and monitor as the
process settles in to steady
state operation. CO may be
high on startup and reduce to

2 Fluke Corporation Carbon monoxide: A mechanic’s approach