Page:NIOSH Manual of Analytical Methods - 6604.pdf/2

 CARBON MONOXIDE: METHOD 6604, Issue 1, dated 15 May 1996 - Page 2 of 3 EQUIPMENT:

REAGENTS:

CO*calibrationgas, 20 to 50 ppm, compressed 1. Carbon monoxide monitor: Envirocheck I single sensor CO Monitor (Quest Technologies); gas cylinder, appropriate pressure regulator, CO262 or STX70 (Industrial Scientific); MiniCO and other items as recommended by (MSA); or other electrochemical CO monitor manufacturer for field check of monitor with equivalent performance specifications. response. 2. Personal sampling pump, 0.250 L/min, with inlet and outlet, used for bag filling and sample analysis when off-site analysis is needed. 3. Air bags, aluminized, 2-L, or other appropriate sizes (optional). 4. Replacement batteries or battery recharger, as appropriate for monitor.
 * See SPECIAL PRECAUTIONS

1.

SPECIAL PRECAUTIONS: Carbon monoxide is a highly flammable, dangerous fire and explosive risk, and is toxic by inhalation. Shipments of compressed calibration gases must comply with 49 CFR 1992 regulations. SAMPLING AND MEASUREMENT: 1.

2. 3.

Zero monitor with CO-free air at the same temperature and relative humidity as the work environment, if possible. NOTE: Monitors are more sensitive to temperature variations than to humidity variations. Most monitors have temperature compensating circuitry . For personal monitoring, locate the monitor as near the worker’s breathing zone as possible. For area monitoring, locate monitor in an area with good air circulation about 60 to 70 inches above the floor. NOTE: Make sure the sensor is not obstructed in either application.

CALIBRATION AND QUALITY CONTROL: 4.

5.

Calibrate with a standard calibration mixture of CO in air from a pressurized cylinder at the CO level recommended by the monitor manufacturer (Normally, 20 to 50 ppm CO). The monitor should be calibrated at the temperature and relative humidity as near as possible to that of the work environment in which it will be used. Check the calibration daily and recalibrate whenever the monitor reading varies from the span gas by 5% or more, or as the manufacturer recommends.

CALCULATIONS: 6.

Read concentration directly from the monitor display. Some monitors (data logger models) will maintain a continuous record of the data as it is accumulated and will calculate the Average, TWA, Peak, etc. concentrations. These data may be read from the display at any time. Some monitors will also store this information for downloading to a computer or printer at the end of the monitoring period. Other monitors only display the current reading, requiring the operator to manually record the data. All monitor models are equipped with alarms that will warn the user (audibly, visually or both) whenever the concentration of CO exceeds the preset level of the alarm. Many are equipped with two-level alarms [3].

EVALUATION OF METHOD: The performance of six direct-reading carbon monoxide monitors was evaluated over a period of 12 months NIOSH Manual of Analytical Methods(NMAM), Fourth Edition, 5/15/96