How to test for combustible gas or flue gas leaks: This document explains how to use the TIF 8800 combustible gas analyzer and similar equipment, outlining methods used to test for the level of toxic and other gases in buildings and in outdoors.
In related documents we give references and explanation regarding toxicity of several of the most common indoor gases, based on literature search and obtained from the U.S. government and expert sources. We include reference links to many articles that can help diagnose the source of dangerous carbon monoxide in buildings.
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Flue gas detectors and combustible gas analyzers such as the TIF8800 discussed here can add an additional level of testing for dangerous gas leaks, flue gas leaks, and assist in detecting leaky chimneys or unsafe gas or oil fired heat exchangers.
This text may assist readers in understanding these topics. However it should by no means be considered exhaustive.
We include safety warnings about relying on any instrument to detect flue gas leaks, natural gas leaks, LP or propane gas leaks, etc.
In our photo at left the TIF 8800 combustible gas analyzer is being used to check for flue gas spillage at the built-in draft hood intake at a gas furnace.
Watch out: Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases.
The photograph at left shows our TIF 8800 combustible gas analyzer being used to sniff for possible sewer gases at an industrial sink. Just about any building drain at a sink includes a local plumbing trap that will produce low levels of detectable gases.
[Click to enlarge any image]
The TIF 8800 gas detection instrument is very sensitive to a wide range of combustibles and hydrocarbons, and is a quick and reliable way to check for gas leaks at LP or natural gas lines as well as for flue gas spillage.
An audible signal which makes a "geiger-counter"-like ticking noise will speed up as the sensor is moved closer to a leak source. This permits the user to not only detect that a combustible gas leak is present, but to follow the gas leak concentration to its source.
The difficulty of making sense of sensitive gas test instrument readings is illustrated by our photographs just above. Called to track down "chemical odors" in a New York law office we found that all of the offices in a one story building shared a common ceiling plenum through which HVAC return air circulated.
At the opposite end of the building from the law office was a beauty parlor whose chemicals proved to be the odor source. Checking the sink (above left) where chemicals were used gave a strong reaction from our TIF8800, but the main chemical source proved to be a closet in which loosely-capped, leaky, and even spilled chemical bottles were stored (above right).
The user can adjust the actual field sensitivity of the instrument using a knob visible at the lower right of the silver control panel in the photograph. The TIF instrument company rates the instrument as responding to very small traces of combustible gases, from 50 PPM to 1000 PPM.
When checking gas piping for leaks, if the plumber has recently sealed a connection using certain pipe sealants containing aromatic hydrocarbon solvents, this instrument will respond just as if there were a gas leak.
It's a fabulous tool when used with thought, and it has often found gas leaks that were otherwise missed by the soap or match (dangerous) method used by many plumbers.
To maximize the sensitivity of the TIF8800 and thus its ability to detect combustible gas leaks, we recommend turning on the instrument while outside in fresh air (and away from any running automobiles or similar equipment).
Let the instrument stabilize, adjust it for a steady but fairly sensitive beeping tone, then enter the area to be inspected.
Following a warm up period (electrode in the sensing tip has to heat up) an adjustable dial sets a tic noise to a steady but modest rate. The manufacturer says to use a rapid rate - which is a more sensitive setting.
As the sensing tip is moved into test locations the operator listens for an increase in the tic rate. The faster the tic the higher the concentration of whatever is being detected.
Your breath will make the instrument respond, even if you're sober - because of its humidity. Gas leaks in any serious quantity will promptly change the tic rate to a continuous siren.
If the siren sounds before the leak source can be identified, the air in the area is contaminated with heavy concentrations of gas. The user can desensitize the tip by turning the control knob to a slower tic rate. When looking for small leaks, a high tic rate must be used.
At CO DETECTION OPTIONS we expliain in detail that when using any gas detector tool to test inside of the air plenum of a fossil-fuel fired appliance as a screen for CO or flue gas leakage, a critical test time is before the blower fan has come on. That's because once the fan begins not only is building air in the plenum diluted, the pressurization of air around the heat exchanger may change the direction of a combustion gas leak.
When using the TIF 8800 or similar gas detectors, remember to test the air for combustible gases at various levels or heights
As we illustrate below, test building air at floor, mid-room height, and near the ceiling, since despite the varying weights of gases (such as LP gas and natural gas), a combustible gas or flue gas might be found at an unexpected location.
For example, flue gases that should be heavier than air and should be found accumulating at floor level may in fact be accumulating at ceiling level in a building where they are carried while mixed with other hot or warm combustion air products (which rise by natural convection).
Our sketches illustrate at least three test locations that should be checked when using a CO detector or a Combustible gas detector (like the TIF-8800)at a heating appliance.
We test at the appliance, we test at the floor (heavier-than-air gas mixes including LP gas), and we test near the ceiling (warm air such as leaky flue gas rises). You may find surprising results.
We inspected a property that had suffered an LP gas explosion and damage. An screened porch was enclosed by solid walls in its lower half. An LP tank stored there was attached to a portable barbecue unit and was leaking.
The property owner opened the kitchen door to access the screened porch whose lower half was filled with LP gas. When the kitchen door opened and a kitchen light switch was operated, LP gas that had entered the kitchen from the porch exploded.
Also see HEAT EXCHANGER LEAK ALLOWED - separate article
Because the TIF 8800 responds to a very wide range of combustible gases, it is useful in tracking down sewer gas or septic gas odors as well. See
Our photo shows Con Edison workers performing gas line replacement & repair work on Washington Avenue in Brooklyn, NY in April 2015. I have this detector and it is giving a positive reading near a taped off sprinkler in the ceiling of a closet and also in my HVAC vents near the ceiling... my landlord says this is normal and that the meter is just overly sensitive, but I purchased this because I sometimes smell gas in this closet and sure enough the meter gives a positive as well. Any suggestions for how I should proceed when I'm being told that everything is fine even when I have a meter reading gas? - Anon. 1/24/2014
Anon: Thank you for an excellent question.
Our photo shows Con Edison workers performing gas line replacement & repair work on Washington Avenue in Brooklyn, NY in April 2015.
In June 2015 the National Transportation Board concluded that in 2014 a large explosion in East Harlem in Brooklyn NY that destroyed two five-story buildings and killed eight people was probably caused by a poorly welded joint in a Con Edison gas line and a break in an old city sewer line.
The Tif 8800 is a very very sensitive device. It will "respond" if you simply breathe on the tip when the instrument is on and warmed-up. It will also respond to VOCs emitted by pipe dope, paint, and a very wide range of VOC-emitting substances besides "gas" that you name in your question. In the product literature you can see a list of the types of substances to which the device is sensitive.
You will want to take a look at two companion articles listed in the article above
GAS DETECTOR WARNINGS and also TIF 8800 FIELD TEST
Now: to demonstrate that the instrument is probably responding to a combustible gas or VOC mixed in air in a building you will want to:
During these tests do not place the sensor tip closer than a foot from plumbing fittings, HVAC controls, or other components that may have used pipe dope, sealants, or other VOC emitting materials. The object is to be sure we are examining air in the test area, not a local emission from a basically harmless sealant or component.
It is also useful to keep in mind that
if combustion gases are emitted inside a building, say from a leaky chimney, they tend to be more concentrated near the ceiling (warm air rises) even though individual gases may be described as "heavier than air" they may rise to the ceiling because they are not existing in pure state but rather are mixed
Also keep in mind that gases other than combustion fuel (LP or natural gas) can cause the instrument to respond. Examples include
Yes and No.
If the instrument responds we don't know just which gas it is responding-to as it is very sensitive to a wide range of hazardous and combustible gases. However, as carbon monoxide released from a heating appliance such as a furnace, boiler, or water heater is being produced by gas (or possibly fuel oil, kerosene, coal or other bio fuel) it is not going to be produced in pure nor isolated form.
Rather the CO (carbon monoxide) will be mixed with leaking or spilling flue gases.
For this reason alone, in our OPINION the detection of abnormal flue gas spillage would be a sufficient indicator of unsafe conditions in a building regardless of the absolute level of carbon monoxide in the mix at that moment.
What the heck is "abnormal flue gas spillage?" Well it's normal for there to be a brief burp or spill of flue gases from many heating appliances at the time of burner start-up and before the chimney has become heated enough to establish full draft. Certainly after a few minutes (five minutes is a reasonable rule of thumb for most residential buildings) there should be no ongoing flue gas spillage at the appliance.
Our photo at left shows a dangerously leaky heating flue - in this case it was visually obvious and no flue gas detection equipment was necessary.
Watch out: when inspecting and testing furnace heat exchangers for leaks, don't forget to look for other flue gas or carbon monoxide leak sources such as shown in our photo at left. Failure to observe a gross safety hazard such as this one risks focusing on the wrong hazard.
False positive gas test results: The TIF8800, for example, is a wonderfully sensitive instrument and it can detect very low levels of flue gas or combustible gases.
But it will also respond to other substances that are miscible in air. Just try breathing on the sensing tip when the instrument is set to a sensitive position and you'll get a response. So test instruments work best in the hands of a very experienced building investigator and instrument user.
False negative results: any gas detection instrument is vulnerable to variations in building conditions or in the operation of mechanical systems in the building that can temporarily hide the presence of a dangerous gas leak. For example, a leaky heat exchanger in a heating furnace may leak detectable gases into the warm air plenum only until the blower fan comes on. Changes in building pressures, open or shut windows or doors, fans on or off, and other such variables can completely change the detectable presence of a dangerous gas indoors.
For this reason, if you call a fire department or emergency worker to test a building for the presence of a dangerous gas such as flue gases, leaks in natural or LP or propane gas lines or equipment, or carbon monoxide levels, even if the worker detects no gas leak present at the time of the inspection that is not a guarantee that the building is safe.
What should you do about this gas test reliability problem? Where there are reasons to be concerned about unsafe gas levels in a building, a more thorough building investigation is in order. Such an investigation includes at least
Readers should see GAS DETECTOR WARNINGS for additional recommendations.
(Oct 9, 2011) Anonymous said: where to get it repaired?
Reply: Anon when my TIF instrument needed repairs I contacted TIF Instruments and then arranged to send it to them for repair work - the results were fine.
TIF instruments and other gas detection equipment are also sold by home inspection tool and equipment suppliers, plumbing and heating suppliers, and test equipment suppliers in most countries of the world. Examples include
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(Jan 24, 2014) Anonymous said:
I have this detector and it is giving a positive reading near a taped off sprinkler in the ceiling of a closet and also in my HVAC vents near the ceiling... my landlord says this is normal and that the meter is just overly sensitive, but I purchased this because I sometimes smell gas in this closet and sure enough the meter gives a positive as well. Any suggestions for how I should proceed when I'm being told that everything is fine even when I have a meter reading gas?
Anon, thank you for the question; I've posted a detailed answer in the FAQs section at the bottom of the article just above. Let us know if you have further questions and let us know what you find.
(Aug 23, 2014) Ken said:
I'm using a combustable gas leak detector (UEi CD100A) to help track down the source of odors/a possible gas. I understand that other procedures also need to be used. After calibrating the detector outside to several clicks per second, I walk down the stairs to the basement. The rate of the clicks double at the bottom of the stairs, are 3 to 4 times the calibrated rate along the baseboard of an outside basement wall, very fast (but not a siren) in a closet ceiling (near electrical conduit - I think) and highest through the opening of a sump pump cover (the water in the sump pump has some vegetation/debris but is otherwise clear). Is the detector most probably just detecting water vapor (e.g. water seeping up from the foundation by the base board) or a gas that could be of concern.
Ken, the UEi CD100A combustible gas detector is, similarly to the TIF 8800 discussed here, responsive to a wide range of gases including Acetone Industrial Solvents Alcohol Jet F uel Ammonia Lacquer Thinners
Benzene Methane Butane Naphtha Ethylene Oxide Natur al Gas Gasoline-P
etrol Propane Halon Refriger ants Hydrogen Sulfide and finally, Toluene.
Some of these instruments will thus respond even to human breath, to airborne dust, to pipe dope, or in the case you describe, decaying vegetation, algae, methane, sewage gas, even maybe water vapor.
The company includes this instrument usage advice that might help in the case you describe:
The audible tic increases in volume when exposed to gases with 50 parts per million or more. When gas is detected, the tic r ate will increase, rotate the thumbwheel back to the steady tic, resetting the instrument to this new background level. Move the instrument into higher concentrations of gas (indic ated by increase tic rate) until the leak is found.
I'd consider where the instrument was responding, its response level, its response to similar mechanical system components in the same building, the presence of obvious emitters that might trigger it, its response at different room elevations, in fresh air, and I'd inspect visually closely any area where I see a response. If there were a leak in a gas pipe you would usually find the instrument response soars significantly when you get close to the leak point (or to a pipe joint with VOC-emitting compounds); most but not all such leaks can be confirmed with a soap solution.
Keep us posted
(Dec 12, 2014) Richard Bowen said:
tif 8800 lost manual, how do the batteries get installed?
This unit has a large recessed screw in a panel on the back side of the device. Opening that screw permits removing of the panel cover to expose the factory's rechargable battery pack.
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