Accurately Measure Flammable Gases

Today, there are a variety of sensors used to detect flammable gases. There are also many different flammable conditions, each requiring a specific type of sensor to be accurately measured. When selecting a flammable gas monitor, it is critical that you understand the differences and choose the appropriate sensor for the environment to be measured.

LEL and UEL Ranges
LEL UELThe familiar “fire triangle” advises us that three things are needed to support a fire or explosion:

  • Source of fuel (e.g. flammable gas or vapor)
  • Air (oxygen)
  • Source of ignition (e.g. spark, open flame, or high temperature surface)

Many commonly encountered gases and vapors (natural gas, methane, propane, hydrogen, alcohols, etc.) are flammable within a range of concentration known as the explosive or flammable range. This range is defined by the lower explosive limit (LEL) and upper explosive limit (UEL) and is different for each flammable gas. For methane, the LEL and UEL in air are 5.0 % and 15.0 % by volume, respectively [NFPA reference]. At concentrations below the LEL, the mixture is too lean (insufficient fuel with respect to oxygen) to sustain combustion, and at concentrations above the UEL, the mixture is too rich (too much fuel with respect to oxygen) to sustain combustion.

Safety instruments using catalytic bead type sensors are intended for use below the LEL, and typically scaled from 0-100 % LEL. This means that the full-scale indication on the monitor is the minimum concentration that could sustain combustion.

LEL RangeMonitoring Above the LEL Range
While most safety-related instruments focus on the sub-LEL range, there are many applications or industries where it is necessary to measure concentrations of flammable gases and vapors above the LEL. For instance, a utility company trying to pinpoint a gas leak may subject its leak detector to concentrations far above the LEL. Another common application is in landfills, where inspection wells are monitored to track the condition of the landfill or to verify that methane produced in the fill is not migrating off site. In monitoring of these inspection wells, concentrations of methane can be well above the LEL or even above the UEL and are often deficient in oxygen.

For these situations, a catalytic bead type LEL range detector is not suitable, and can indicate dangerously low false readings. Remember, the catalytic bead type sensor must “burn” the gas on the surface of the bead. If the mixture is above the UEL (too rich), the instrument may actually indicate a very low reading or no reading due to insufficient oxygen. In addition, subjecting a catalytic bead sensor to very high gas concentrations can result in damage to the sensor, including loss of sensitivity that can also produce erroneously low readings.

For applications of this type, where very high gas concentrations may be encountered, the most commonly used method of detection is thermal conductivity (TC).

Thermal Conductivity
A thermal conductivity detector is based on the principle that gases differ in their ability to conduct heat.

A TC detector will consist of two elements, typically a pair of wires (filament) or thermistors that are heated above ambient temperature. One of the elements (active) is exposed to the gas sample to be measured, and the second element (reference) is exposed to a reference gas (typically air for this type of instrument).

If the sample gas has a different thermal conductivity as compared to the reference gas, the temperature of the active filament will change as compared to the reference element. As with the catalytic bead type sensor, the resultant temperature change results in a resistance change that is measured with a Wheatstone bridge circuit to produce a digital reading proportional to the gas concentration.

The TC sensor can be used for a variety of gases, and does not require oxygen to operate. Because the thermal conductivity of different gases as compared to air can vary widely, and be either positive or negative in direction, the thermal conductivity detector must be tuned or calibrated for a specific gas or vapor. The most notable advantage of the TC type detector is it’s ability to detect concentrations of flammable gases and vapors up to 100 % by volume, well above LEL and UEL ranges.

Gas Monitoring for Ballast Water Treatment

Marine Oil TankersThe Issue

Since the development of steel hulled vessels around 120 years ago, water has been used as a ballast material to stabilize vessels at sea. Ballast water is pumped-in to a vessel to maintain safe operating conditions throughout a voyage.  This practice reduces stress on the hull, provides stability, improves propulsion and maneuverability, and compensates for weight loss due to fuel consumption and other factors.

While ballast water is essential for safe and efficient modern shipping operations, it may pose serious ecological, economic and health problems due to the great variety of marine species carried in ships’ ballast water. These include bacteria, microbes, small invertebrates, eggs, cysts and larvae of various species. The transferred species may survive to establish a reproductive population in the new host environment, becoming invasive, out-competing native species and multiplying into pest proportions.

The problem of invasive species in ships’ ballast water is largely due to the expanded trade and traffic volume over the last few decades and since the volume of seaborne trade continues to increase, the problem may not yet have peaked. The effects in many areas of the world have been devastating. Data show that the rate of bio-invasions is continuing to increase at an alarming rate and new areas are being invaded all the time.

The spread of invasive species is now recognized as one of the greatest threats to the ecological and the economic well being of the planet. These species are causing enormous damage to biodiversity and the valuable natural resources of the earth. Direct and indirect health effects are becoming increasingly serious and the damage to the environment is often irreversible.

How the Issue is being addressed

In 2004, the International Maritime Organization (I.M.O.) adopted the Ballast Water Control Treaty to require the installation of BWT systems into commercial marine vessels around the world.  Basically, all new ships built since 2012 must have a BWT system.  And existing ships built prior to 2012, must have a BWT system installed by 2017.  This involves approximately 70,000 ships worldwide that must comply with the treaty.  And, there are approximately 2,000 to 3,000 ships being built, annually.

Major Applicable Vessels

  • LNG Tankers
  • Oil Tankers
  • Coal Carriers
  • Chemical Tankers
  • Container Vessels
  • Bulk Vessels
  • Chip Vessels
  • RO-RO Vessels
  • Lumber Vessels
  • Car vessels
  • Passenger Ocean Liners & Cruise Ships

Ballast Water Treatment Methods

There are a variety of methods that have been proposed and utilized with varying degrees of success to eliminate the organisms in a vessel’s ballast tanks and ballast system.

They are:

  • Ozonation (Ozone)
  • Electrolysis (Electro Chlorination = Hydrogen & Chlorine)
  • Reagent Transfusion (Sodium Hypochlorite = Chlorine)
  • Inert (Removing Oxygen)
  • UV  (Ultraviolet Light)

Due to the varying degrees of efficiencies for each of the above methods with respect to results versus the volumes of water that can be effectively treated and the energies required, the two most popular

Methods are

  • Electro Chlorination
  • Ozonation.


Pumping Stations Require Fixed Gas Detection for LEL

There are many thousands of gas compressor stations that present the constant potential hazard of accumulating combustible gases.

Application Description

As natural gas is moved through transmission pipelines from its source to markets in other parts of the country, the pressure needs to be boosted periodically. This typically occurs every 50 – 75 miles. At these intervals, gas arrives at stations where the gas is re-pressurized by a compressor. These facilities are referred to as compressor stations. Each of these stations has applications for gas detection and RKI Instruments has products that are ideally suited to these requirements.

event Facility Types
There are basically two types of compressor stations: The large compressor station which houses many compressors inside a (usually metal) building which is often open on both ends and has an air gap between the building and the slab.
The other is skid mounted with one compressor on a slab and may be open or be covered with a metal carport like cover. The open air compressors seldom have onsite gas detection.

Who to Call On
Facilities: Transmission and distribution gas pipeline companies.
People: Operations Engineer, Instruments Engineer or Compressor Maintenance Supervisor. These people are generally located at a corporate or regional office or at the station itself. For prospecting purposes, stop by the station and ask who is responsible for their fixed gas detection instrumentation. Compressor stations can be found on the company web site under “assets map”.

RKI Solutions
Compressor stations generally consist of a small hut that houses the compressor as well as various gauges, valves, flanges etc. which can be sources of potential leaks.

Stationary sensors for the detection of combustible gases are necessary to be placed directly above the compressor. The compressor generates a significant amount of heat and the point of detection can easily reach 140 degrees Fahrenheit or more. Our M2 is especially well suited for this. The sensor can be mounted remotely from the transmitter and be installed directly above the compressor. The transmitter itself is mounted at location convenient to the operator- typically on a wall at eye level. A calibration cup is often mounted permanently to the sensor and tubing is run down next to the sensor head. In this manner, a calibration can be completed easily and safely while maintaining the ideal placement of the sensor itself.

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Wastewater Gas Monitoring System, Explosion Proof Tri-Sensor Head

RKI’s tri-sensor head is designed for detection of the hazardous gases typically encountered in wastewater and wet well type applications. The combination sensor head includes reliable long-life sensors for H2S, O2, and flammable gases, as required by NFPA 820 for sewage and wastewater treatment facilities. The sensor housings and tri-sensor head enclosure are 316 stainless steel to provide durability in harsh environments. Optional splash guards are also available for wet or dusty locations.

This unique tri-sensor design integrates 3 sensors into one unique explosion proof housing. This lowers the installation and wiring cost versus traditional single sensor enclosures. Only one conduit needs to be run to the sensors.

This product is also available in a two and four sensor version, with sensors for LEL, Oxygen, H2S, CO, or CO2. Catalytic bead (“pellistor”) and NDIR (non-dispersive infrared) sensor versions are available for LEL detection.

The Beacon 410, four channel, wall mount controller digitally displays the gas name, readings, and status for up to 4 channels. Each channel has 3 fully configurable alarm points. Each channel also has 2 dedicated individual relays for activating external devices like alarm horns, strobes, pumps, fans or other electrical devices. A bank of 5 common relays are also standard. The Beacon 410 powers up to four remote sensors or transmitters.

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Hydrogen gas is looked to as a cleaner source of energy for the future. It is also commonly used in many industrial processes. Hydrogen is one of the most explosive gases, and leaking hydrogen cannot be seen or smelled.

RKI Instruments, Inc. offers a unique technology for detecting dangerous levels of hydrogen gas. This technology utilizes a proprietary process to produce a sensor that is selective to hydrogen (no false alarms from other gases or vapors) and virtually immune to traditional catalyst poisons. For instance, semiconductor operations need to detect hydrogen without experiencing nuisance alarms from cleaning solutions containing isopropyl alcohol. Glass manufacturing processes need to detect hydrogen, but also involve silicone, which can poison traditional catalytic bead sensors. RKI’s hydrogen specific sensors are ideal solutions for applications like these.

Special Monitoring Solutions for Refineries

Limited Hot Work

RKI’s GP-03, a portable single gas combustible monitor, is being used to minimize the permitting process for what is called, Limited Hot Work. Refineries in Northern California eliminate the need to pre-test areas by using the GP-03 gas monitor.

Limited Hot Work is when any electrical device like laptops, PDA’s, pagers, and cell phones are used in a Class 1, potentially hazardous, flammable or explosive environment. Since these items are usually not intrinsically safe, there is a protocol covering the use of these items at refineries. When any employee or contractor is using any of the above-mentioned items at a refinery, they are issued a portable LEL meter (like the GP-03). As long as the GP-03 is not in alarm (below 10% LEL), it is OK to operate the electrical device.

Method 21 for Tanks with Inert Enclosures
eventThe GP-03’s size and price make it an ideal hands free solution for Limited Hot Work. Measuring only 2.6 inches tall and weighing only 2.8 ounces, the GP-03 is literally the smallest single gas combustible monitor in the world. With a low price and a two year warranty, it’s also the best value on the market. All GP-03’s are equipped with a rubber protective boot and alligator clip.Method 21 for Tanks with Inert Enclosures
Method 21 is an EPA protocol for monitoring VOC leaks to ensure that those emissions are kept within certain levels to control air pollution. The EAGLE is being used extensively at refineries in Northern California to comply with Bay Area Air Quality Management District (BAAQMD) mandated emissions monitoring. For refineries that have storage tanks with an inert enclosure, monitoring the inert space for hydrocarbons with an instrument that complies with Method 21 is required. RKI has configured an EAGLE specifically for this application.The part number for this particular version of the EAGLE is 72-5101RK-11T and is described as an EAGLE with catalytic sensor (ppm/LEL), internal dilution to add fresh air (oxygen) to the catalytic sensor, and a Teflon sample hose to accommodate the heavier hydrocarbon samples. The EAGLE has been extensively tested against flame ionization detectors (FIDs), which is the most widely used monitoring technology for Method 21. The EAGLE complies with Method 21, is less expensive than an FID, and can be operated for longer periods of time (30 continuous hours on 4 D size alkaline batteries). Also an FID cannot be used for this application due to the inert gas background.

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Purge / Test procedure using model GX-2012

When new natural gas mains are installed or existing mains removed from service, crews must purge the mains with an inert gas to eliminate the potential hazard of a combustible mixture. The most commonly used and preferred purge gas is nitrogen. After the purge is conducted an upstream valve is opened to allow natural gas to enter. A service valve on the line with a stand pipe or diffuser attached is cracked to allow venting gas or nitrogen to escape.

When measurements are taken at stand pipe or diffuser with service valve cracked, RKI recommends use of our “T” fitting adapter, p/n 17-4430RK-01 (as pictured below), for purge testing.

A standard confined space instrument will not adequately test for safe conditions during this process, as the high gas level will overwhelm or damage an LEL sensor, and the sensor will not function in an oxygen-depleted (inert) atmosphere. The RKI Model GX-2012 has been specifically designed for this application, utilizing a robust thermal conductivity (TC) sensor that can measure high gas levels without damage, and does not require oxygen for accurate measurements.

For existing main:

  1. Purge line with N2. Use GX-2012 in % Vol only (purge) mode (also measures O2) to verify that O2 reading is 0.5 or less, and gas reading 2% or less, to verify purge.
  2. Open line and perform service. This will introduce air into the main.
  3. Purge again with N2. Use GX-2012 in % Vol only mode (also measures O2) to verify that O2 reading is 0.5% or less.
  4. Open upstream valve to charge line with gas. Use GX-2012 in % Vol only mode (also measures O2) to verify that gas reading is 98% or more.

For new main:

  1. Purge line with N2. Use GX-2012 in % Vol only mode (also measures O2) to verify that O2 reading is 0.5% or less, to verify purge of air from line.
  2. Open upstream valve to charge line with gas. Use GX-2012 in % Vol only mode (also measures O2) to verify that gas reading is 98% or more.

All measurements taken at stand pipe or diffuser with service valve cracked. RKI recommends use of our “T” fitting adapter (p/n 17-4430RK-01) for purge testing.

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Monitoring for Inert Spaces

An inert space is one that has been purged with engine exhaust, nitrogen, or other gas mixtures not containing oxygen. It is a common practice on board ships to purge the headspace above petroleum-based product, or in empty product storage spaces to prevent the accumulation of a flammable mixture in the space. For a flammable mixture or fire to exist there are 3 necessary components: fuel, oxygen, and heat or ignition. This is often referred to as the Fire Triangle. By removing the oxygen from the space, it eliminates one of the three necessary components thereby preventing the possibility of a fire even if flammable vapors are present. In other words, if there is no oxygen present, there cannot be an explosion.

For these reasons it is important to know both the level of hydrocarbon vapors and oxygen present in the headspace or empty tank. The level of hydrocarbon or flammable vapors in these types of spaces will often exceed the LEL (lower explosive level) and can even be in the percent volume range. It is also important to monitor for oxygen concentrations in these types of spaces to assure a good purge.

The most common type of meter used to test for flammables utilizes a catalytic type sensor, which will sense combustible gases at LEL levels. This type of catalytic sensor requires oxygen in order to function. If there is no oxygen, or a very low oxygen level is present, the catalytic sensor will not work. The meter will give false readings and a false sense of security. Sometimes a dilution fitting is used with a catalytic sensor to blend some oxygen in with the sample in order to get around this problem. This method can work but is prone to errors. If the dilution fitting is forgotten or if it is partially or fully plugged, then the operator will get false or inaccurate readings.

Riken Keiki has developed 4 instruments specifically for this type of inert space monitoring, RX-8000. These instruments use an infrared (IR) sensor to measure hydrocarbon vapors over 2 ranges; 0 – 100% LEL and 0 – 100% volume. The RX-8000 will also measure oxygen in addition to the 2 ranges of hydrocarbons.

Unlike the catalytic sensor, the IR sensor is ideal for inert monitoring type of applications because the IR sensor does not require oxygen in order to function. The RX-8000 instruments utilize a dual IR bench to permit accurate testing over the entire range of a target hydrocarbon up to 100% by volume. The dual auto ranging allows the instrument to automatically switch from a 0 – 100% LEL range to a 0 – 100% volume range without any reconfiguring.

Also, for both the single gas model RX-8000 (CH4 or HC) and the dual gas (HC/O2) RX-8000, there are two versions available. For petroleum type carriers like oil tankers, both models are available in a general hydrocarbon (HC) detection version. For natural gas type applications like LNG or LPG ships, both models have a methane (CH4) version. Both instruments come standard with built in sample drawing pumps and are explosion proof with intrinsically safe designs.


Backup Batteries Emitting Hydrogen

battery_testingCustomer Type:

Cellular telephone cell sites, backup battery stations, or any battery rooms.

Application Description:
Since batteries are such an effective energy storage medium for almost any backup power system, many industries use backup battery banks for emergency power. The need for gas monitoring occurs while these backup batteries are being charged. Typically, batteries are continuously trickle charged. After an incident that requires battery use, a higher charge is used to quickly restore the batteries to full capacity. This charging process generates hydrogen gas which is emitted into the battery storage room. The faster the charge rate is, the higher the hydrogen generation rate is.

Backup batteries are normally of the lead acid type, however some are liquid based, gel cells, or even sealed type batteries. No matter which of these battery types they are, hydrogen is generated while being charged.

Hydrogen is a highly flammable gas. The National Fire Protection Association lists the lower explosive level (LEL) for Hydrogen as 4% by volume. If sufficient hydrogen collects in a room, it can potentially explode if ignited. This type of explosive hazard can destroy equipment as well as causing injury or death to personnel. The likelihood of this happening depends on the number of batteries, their charge rate, the size of the room, and the ventilation available for the room. Although this may not be a common occurrence, the potential hazard exists with any type of enclosed backup battery station. This danger can be eliminated by monitoring for a hydrogen buildup, and taking appropriate action if a build up occurs.

RKI’s Solution:
RKI has developed the Model PS2 for this type of application. The PS2 is a low cost, stand alone, continuous gas monitor designed specifically for trouble-free hydrogen gas monitoring. The PS2 uses a long life, low maintenance metal oxide sensor for detection of hydrogen gas. The unit has two alarm levels, typically set to 10% LEL (0.4% volume hydrogen) and 30% LEL (1.2% volume hydrogen). If these alarm levels are exceeded, the PS2 activates a 10 amp relay for each level, and also its own audible and visual alarm. If action is taken at the first alarm level (for example, turning on a ventilation fan in a room to clear out the hydrogen), then the second alarm level should never be exceeded. The second alarm level typically would be used for more drastic action, such as turning on a bigger fan, cutting off the battery charge, or sounding a louder or remote alarm to bring attention to the problem.

The PS2 is a simplified, stand alone fixed system that is easy to install. It comes in a compact wall mounting enclosure, with terminals inside for power and remote alarm connections. The unit can be powered by 24 VDC, or optionally by 115 VAC (which ships with a 6 foot power cable), or 48VDC. Since hydrogen is lighter than air (vapor density for H2 is 0.1), emissions will typically rise. The PS2’s sensor is on the end of a 30 foot cable, so that it can be mounted above the batteries. RKI recommends that a yearly check of sensor response is performed. A low cost calibration kit is available through RKI that will deliver a small amount of hydrogen to the sensor and confirm that the sensor will go into alarm. The PS2’s metal oxide sensor has an extremely long life-span. It is not uncommon for this sensor to last 5 to 10 years or even longer. The PS2 is an economical, trouble-free solution that is ideal for monitoring battery rooms.

Oxygen Deficiency Monitoring in Hospitals

The Issue:
Hospitals use and store large quantities of industrial and medical gas cylinders and containers; one common container is for liquid nitrogen. Liquid nitrogen provides temperatures as low as -196°C and it can be used for cryobiology and cryotherapy. The low temperature is used in cryoconservation for the long-term preservation of blood, blood components, other cells, body fluids or tissue samples.

The presence of nitrogen cylinders and containers requires a focus on safety. Liquid Nitrogen rapidly vaporizes to gas at about 700 times the liquid volume. By displacing air the gas may kill by asphyxiation. When the oxygen concentration in air is sufficiently low, a person can become unconscious without any warning symptoms.

RKI’s Model OX-600, stand alone oxygen monitor units, can monitor individual rooms that store nitrogen containers. An optional remote mount sensor and cable can be equipped which allows the unit to be mounted on the outside of the room, in the hallway, while the extender cable allows the sensor to be located in the area with the nitrogen containers. This allows a person to recognize the condition of a room storing nitrogen prior to entering. Being aware of oxygen deficiency in the presence of compressed nitrogen cylinders or liquid nitrogen containers can save lives.

OX-600_bThe OX-600 is an indoor, standalone monitor that detects Oxygen (O2) with a range of 0-25.0 % volume with 0.1% increments. Its sleek, low profile design is equipped with a unique tri-color display, which changes color as oxygen levels reach each alarm level. The OX-600 has 2 preset alarms, and comes ready to operate with a simple wall mount bracket and 10 foot power cord. It is capable of operating with three different power options: 115 VAC, 24 VDC or alkaline batteries (in Canada, only the 24 VDC and alkaline versions are available currently). If Oxygen is present, the user is notified by an audible alarm tone and the multicolored LED digital display.

The OX-600 uses a fast responding low-cost plug-in style galvanic cell sensor. This long life sensor is field- replaceable with no special tools required. The sensor can also be remotely mounted when instrument is supplied with optional sensor cable.

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Transformer Condition Tested with an H2 Gas Monitor

Application Description
Electrical utilities use large electrical transformers to drop the voltage coming from power lines. These transformers can be huge; the size of a car or greater. The transformers are sealed with an oil bath surrounding all of the electrical coils inside. This oil bath acts as both a coolant and an insulator. At the top of the transformer, there is a headspace that has no oil and instead is filled with nitrogen, generally under a slight positive pressure. For a new transformer, this nitrogen blanket will remain “clean” for a long time. As the transformer ages, and the insulation between the wire coils starts to break down, the high voltage can arc between two adjacent coils of the transformer. When this occurs, the high voltage passes through the oil blanket, and causes the oil to break down. This causes small amounts of flammable vapors to form from the oil, and rise to the top of the transformer to mix with the nitrogen blanket. These flammable vapors consist of a variety of gases, but generally hydrogen is predominant. Periodic testing of the nitrogen blanket for flammable vapors is a good indication of the health of the transformer. If the testing reveals a buildup of flammable vapors, the transformer can be removed from service in a planned manner instead of a catastrophic manner (they can blow up if undetected).

RKI’s Solution

RKI offers “Transformer Gas Testing” versions of our EAGLE portable sample drawing gas monitor for this application. These instruments have a range of 0-5% hydrogen and use a catalytic sensor. This unit also monitors Oxygen. This Eagle for transformer gas testing has two pumps. In this version the probe is connected directly to the transformer tap, and the internal pump is used to extract a sample from the transformer. A second pump is used to pull the required air through the dilution fitting. This version can also be used on transformers with positive or negative pressure. Testing frequencies vary for each Utility, but generally are between 3 to 6 months. A sudden rise of flammables over this time period is an indication of transformer trouble.

  • Available in single H2 or dual gas with H2 and O2 channels
  • Dual pump design eliminates the need for sample gas bags or dilution fittings
  • Increasing O2 alarms
  • LEL, PPM, or % vol H2 readings
  • Takes samples from positive or negative pressure transformers

Ordering Information

Single Gas H2 EAGLE
EAGLE for Hydrogen (H2), 0 – 5% volume with 2 pumps for transformer testing

Calibration kit, EAGLE, 103L cylinder of 50% LEL Hydrogen/Air, demand flow regulator, case & tubing

Dual Gas H2/O2 EAGLE
EAGLE for H2 (0 – 5%) / O2, with 2 pumps for transformer gas testing

Calibration kit, EAGLE, 103L cylinder of 50% LEL H2/Air, 103L cylinder of 100% N2, demand flow regulator, case & tubing

Cal kit, EAGLE, 34L cylinder 50% LEL H2/Air, 34L cyl 100% N2, dispensing valve, gas bag, case & tubing
Takes samples from positive or negative pressure transformers

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Solutions for Landfill Applications

A landfill is a site for the disposal of waste materials by burial. It is the oldest form of waste treatment. Historically, landfills have been the most common method of organized waste disposal, and remain so in many places around the world.

Landfills may include internal waste disposal sites (where a producer of waste carries out their own waste disposal at the place of production) as well as sites used by many producers. Many landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling).

A landfill, by the nature of the wastes placed in it, will generate dangerous gases. These gases can pose serious health and safety problems for operators and the community, both during the operation of the landfill and after it has been closed, so facilities must have landfill gas monitoring and control program plans.

Customer Type
Landfill Owners/Operators

Categories of Monitoring
Monitoring data taken at landfills does not necessarily reflect the levels of contamination to which people may be exposed. However, the data usually offers some insight into general air quality, landfill gas migration, possible health hazards and conditions within the landfill itself. In general, monitoring of gases that emanate from landfills falls into the following categories:

  • Monitoring at gas wells (most common)
  • Soil gas monitoring
  • Near surface gas monitoring
  • Emissions monitoring
  • Ambient air monitoring
  • Protection of structures / enclosed spaces where methane can accumulate

Typical landfill gas composition

% (dry volume basis)*

Methane, CH4


Carbon dioxide, CO2


Nitrogen, N2


Oxygen, O2


Sulphides, disulphides, mercaptans etc.


Ammonia, NH3


Hydrogen, H2


Carbon monoxide, CO


Trace constituents


Eagle2_aRKI’s Solution

The Eagle 2 is rugged, reliable, easy to operate and maintain. It is a great solution for just about any portable gas-monitoring situation. Features below include:

  • Low Cost – Very low cost as compared to standard analytical devices
  • Continuous Operation – The Eagle 2 can operate continuously from a 115 VAC continuous operation adapter. Also, if desired, it can run from alkaline batteries (At 70°F, 18 hours using alkaline batteries, or 20 hours using Ni-MH.)
  • Powerful Pump – The Eagle 2 has a very strong pump and can be provided with a sample hose up to 125 feet long. Powerful, long-life pump (over 6,000 hours) can draw samples over 125 feet. Flow rate approximately 2.0 SCFH. Also, the Eagle 2 can draw against a vacuum of 50” of water.
  • Filters For Dirty Applications – The Eagle 2 is provided with two dust and hydrophobic filters. one is inside the probe and one is a backup filter which is located inside the unit.
  • Alarms – 2 Alarms per channel plus TWA and STEL alarms for toxics. The two alarms are fully adjustable for levels, latching or self-reset, and silenceable. The buzzer is rated at 95 dB at 30 cm, and there are also four high intensity LED’s.
  • Enclosures – Weatherproof, chemical resistant, RFI / EMI coated high impact polycarbonate-PBT blend. Can operate in 2.0” of water without leakage. Ergonomically balanced with rugged top mounted handle. Water & dust resistant equivalent to IP65.
  • Data logging – Standard in all Eagle 2 units, and the data log software is supplied free on the Eagle 2 Product CD which is shipped with each unit.

Eagle 2 Landfill Configurations
We offer many versions of the Eagle 2, which can be customized in terms of the sensors included. Listed below are some of the more common Eagle 2 configurations for use in Landfill gas detection. Please consult the factory for other combinations.

Part Number / Sensors
723-035-05 / CH4 (IR Auto ranging %LEL/%Vol)/O2/CO2 (IR 0-60%)
724-059-05 / CH4 (IR Auto ranging %LEL/%Vol)/O2/CO/CO2 (IR 0-60%)
724-068-05 / CH4 (IR Auto ranging %LEL/%Vol)/O2/H2S/CO2 (IR 0-60%)
725-106-05 / CH4 (IR Auto ranging %LEL/%Vol)/O2/H2S/CO/CO2 (IR 0-60%)

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Refinery Catalyst Dumping Operations

Refineries use large “cracking towers” as a part of their operations. These towers can be approximately 100 feet tall and are filled with a catalyst which assists the conversion of oil into lighter fuels. Periodically, the catalyst must be removed, the tower cleaned out, and new catalyst added. In order to remove the old catalyst, workers must enter and remain inside the tower wearing full protective gear. As the old catalyst is being removed, flammable and hazardous vapors can be emitted. As a result, a gas monitor must be used to monitor the condition of flammable vapors, oxygen levels, and normally H2S and CO also.

Since the tower is purged with Nitrogen, there is ideally no oxygen present. An increase in the volume of oxygen would mean that the Nitrogen purge is not adequate. Therefore oxygen detection is normally set for an increasing alarm between 2% to 4% volume, to warn of an increasing oxygen situation. For monitoring LEL with a catalytic sensor, a dilution fitting must be used, since the catalytic sensor requires oxygen in order to operate. (Note that an IR sensor cannot be used for this application because it is possible that hydrogen could be one of the flammable gases present, and an IR sensor cannot detect hydrogen).

Normally this testing must be done 24 hours a day for several weeks. Although a continuous monitor can be used, quite often portable monitors are used for this application due to their flexible nature and ease of use. The test area is extremely dirty with fine catalyst dust, and so any sample drawing instrument must utilize appropriate filters to avoid pump and flow problems. It’s also important that a gas monitor’s sample drawing pump be able to draw a sample over 100 feet to test deep within the tower.

RKI’s Solution

EAGLE 2 One To Six Gas Portable Monitor:

  1. Eagle2_aContinuous Operation – The EAGLE 2 can operate continuously from a 115 VAC continuous operation adapter. Also, if desired, it can run from batteries and it will operate for 30 hours from 1 set of Alkalines.
  2. Dilution Fitting For Accurate Combustible Readings -The EAGLE 2 can be provided with a removable dilution fitting. This fitting quickly snaps onto the instrument’s inlet fitting, and the hose connects to it. Since this fitting blends 50% sample with 50% ambient air, it provides sufficient oxygen for the Catalytic sensor to operate if the instrument is located in a fresh air environment. The instrument can be calibrated to read directly either with the dilution fitting in place or without the dilution fitting. To read the oxygen level inside the tower, the dilution fitting can either be removed, or the dilution hole can be covered with a finger for a minute to draw 100% sample into the instrument.
  3. Permanent Internal Dilution Fitting – As a special option, the EAGLE 2 can be supplied with a permanent internal dilution fitting. In this case, the dilution is present for the LEL sensor at all times, but the flowpath of the instrument is designed so the dilution does not effect the Oxygen, H2S, or CO readings.
  4. Powerful Pump -The EAGLE 2 has a very strong pump and can be provided with a sample hose up to 125 feet long. Without dilution, a sample will draw through this hose in less than one minute.
  5. Filters For Dirty Applications – The EAGLE 2 has many effective filter options. It can be provided with a probe which contains a sizeable, effective, and easily replaceable pleated paper dust filter. This is essential for this application. In addition, it can be provided with a large hydrophobic and fine dust filter inside the unit as a final stage of protection.
  6. Buzzer Options -The EAGLE 2 can be provided with an extra loud buzzer added in addition to the standard buzzer. This creates noise levels of about 95 db at 3’, to help in high noise areas. Another attention getting option is a remote horn and strobe light on the end of a 20’ cable.
  7. Adjustment Lockout Switch – This switch is located inside the EAGLE 2, and can be used to assure that only authorized personnel have access to set up controls such as calibration and alarm point options.
  8. Weatherproof -The EAGLE 2 is fully water shedding and gasketted by design and is fully functional in the rain. It can also be placed into water several inches deep, while operating, without fear of damage or water entry.

The EAGLE 2 has proven itself at many refineries to perform excellently for this application and to hold up well despite the harsh conditions of use.

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