Basic Air Monitoring Concepts And Use Of The Altair 4 Gas Meter MSA Altair 4 Multi-Gas Meter Explosive Atmosphere Oxygen Concentration Carbon Monoxide Hydrogen Sulfide Photo Ionization Detector Meter using ultraviolet light to detect vapors with low LEL’s, up to 10,000 ppm Colorimetric Tubes Flame Ionization Detector Similar to the PID, but uses a hydrogen flame instead of UV light to detect vapors Used to detect single gases Some Common Haz-Mat Terms Vapor Pressure The 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 Density The 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 Process o Identification of the substance o Placards o MSDS Sheets o DOT ERG guide (Orange Book) o NIOSH Book o Shipping Papers o 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 Range Lower 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 % Methane 0% 5% 15 % 100 % Correction Factors LEL 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 0.5 Hydrogen 0.5 Propane 0.8 Pentane 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 % Oxygen Before 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 Test Calibration 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 LED The instrument is equipped with a green "SAFE LED". This green SAFE LED 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 a successful Bump Test or calibration. Instrument run time 16 hours at 77°F (25 °C) Charging time ≤ 4 hours The maximum safe area charging voltage Um = 6.7 Volts D.C. Temperature range -4 °F to122 °F (-20 °C to 50 °C) operating 50 °F to 95 °F (10 °C to 35 °C) while charging battery A combustible gas reading of "XXX” indicates the atmosphere is above 100 % 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 or toxic gases in the following atmospheres as this may result in erroneous readings: • 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 combustible gases in atmospheres containing vapors from liquids with a high flash point (above 38 °C, 100°F) as this may result in erroneously low readings.