Basic Air Monitoring Concepts

And Use Of The Altair 4 Gas Meter

MSA Altair 4 Multi-Gas Meter

Explosive AtmosphereOxygen ConcentrationCarbon MonoxideHydrogen Sulfide

Photo Ionization DetectorMeter using ultraviolet light to detect vapors with low LEL’s, up to 10,000 ppm

Colorimetric TubesUsed to detect single gases

Flame Ionization DetectorSimilar to the PID, but uses a hydrogen flame instead of UV light to detect vapors

Some Common Haz-Mat Terms

Vapor PressureThe amount of force applied on a container by the

vapors coming from a substance. A vapor pressure greater than 40 mmHg is considered a respiratory

hazard. Water has a VP of inbetween 17 - 25 mmHg.

Vapor DensityThe relative comparison of a material to air. This determines whether the vapors will rise or settle. Air is given a score of 1. If the density is less than one, say .8, the substance will rise. If its say 1.9,

the substance will settle.

The Metering Processo Identification of the substance

o Placardso MSDS Sheetso DOT ERG guide (Orange Book)o NIOSH Booko Shipping Paperso History of event

Getting Started

After turning the meter on in a clean atmosphere.

1. Determine flammability/explosive potential

2. What is the flammable range of the substance you are metering ?

3. This number is usually given as a percentage.

4. What does this number mean ?

Flammable RangeLower Explosive Limit (LEL)

The smallest concentration in air of a substance that will support fire or an explosion

Upper Explosive Limit (UEL)The largest concentration of a substance that will

support fire or an explosion

Example: Methane LEL = 5 % UEL 15 %

5 % 15 %

Methane

100 %0 %

Correction FactorsLEL sensors are calibrated to a certain gas, in our case pentane. The catalytic bead LEL sensor will

respond to other gases as if they are pentane. So what do we do if we are metering something other than

pentane ?

We use correction factors ! Yeah !

What are the correction factors for our meter ?

Methane 0.5Hydrogen 0.5Propane 0.8Pentane 1.0

Take your explosive reading and multiply by the numbers on the left to get your reading.

If your meter shows 25 % of the LEL and you are monitoring methane, multiply 25 x 0.5, so the actual reading is 12.5 %

OxygenBefore entering the atmosphere to be metered, the

oxygen concentration should be in the normal range, approximately 20.8 %. Concentrations above 20.8 % and below 19.5 % should be considered dangerous

and the area left as soon as possible.

Calibration Vs. Bump TestCalibration

Putting the meter into a ‘calibration mode’ and making sure the meter reads within a specific range of a known gas and if not, making necessary adjustments to correct.

Bump Test

Attaching the meter to a known source of gas and making sure the meter alarms with the appropriate

numbers.

Altair 4 Operation

Safe LEDThe instrument is equipped with a green "SAFE LED". This green SAFELED flashes every 15 seconds under the following conditions:• the SAFE LED feature is enabled• instrument is in Measurement Mode (Normal Operation)• combustible reading is 0% LEL or 0.00%CH4• Oxygen (O2) reading is 20.8%• Carbon Monoxide (CO) reading is 0 ppm• Hydrogen Sulfide (H2S) reading is 0 ppm or 0 mg/m³• no gas alarms are present (low or high)• instrument is not in Low Battery warning or alarm• CO, H2S, STEL and TWA readings are 0 ppm or 0 mg/m³.

The √ symbol will be displayed in the Measure mode for 24 hours after asuccessful Bump Test or calibration.

Instrument runtime 16 hours at 77°F (25 °C)Charging time≤ 4 hoursThe maximum safe area charging voltageUm = 6.7 Volts D.C.Temperaturerange-4 °F to122 °F (-20 °C to 50 °C) operating50 °F to 95 °F (10 °C to 35 °C) while charging battery

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A combustible gas reading of "XXX” indicates the atmosphere is above100 % LEL or 5.00 % vol CH4, and an explosion hazard exists.Move away from hazardous area immediately.

Do not use the ALTAIR 4 Multigas Detector to test for combustible ortoxic gases in the following atmospheres as this may result in erroneousreadings:• Oxygen-deficient or oxygen-rich atmospheres• Reducing atmospheres• Furnace stacks• Inert environments• Atmospheres containing combustible airborne mists/dusts.

• Do not use the ALTAIR 4 Multigas Detector to test for combustiblegases in atmospheres containing vapors from liquids with a high flashpoint (above 38 °C, 100°F) as this may result in erroneously lowreadings.