Atmospheric Monitoring

ATMOSPHERIC MONITORING INSTRUCTIONAL GOAL The participant will understand the need for atmospheric monitoring and the types, uses, and limitations of various monitoring devices.

ENABLING OBJECTIVES Identify at least four types of monitoring devices and their use. List the three main atmospheric conditions that cause the greatest concern for confined space entries. Explain the order in which confined space monitoring is to be conducted.

Air Monitoring Must conduct atmospheric monitoring of permitted space prior to entry. Primary purpose of air monitoring is to determine whether conditions are acceptable for entry.

Air Monitoring Entry into a confined space is prohibited until initial testing of the atmosphere has been performed. Person assigned the task of atmospheric monitoring must be versed on the operation and limitations of the specific instrument used.

Testing & Monitoring Three main atmospheric hazards that cause concern :  Oxygen depletion  Flammability  Toxicity Monitors are very specific. There is no universal monitor that can test for all possible gases.

Monitor Characteristics Easily operated Easily operated Readable in both light and dark conditions Readable in both light and dark conditions Easily calibrated or standardized Easily calibrated or standardized Equipped with a peak-hold feature to record the highest concentration encountered Equipped with a peak-hold feature to record the highest concentration encountered Equipped with audible and visual alarms for a preset concentration Equipped with audible and visual alarms for a preset concentration

Monitor Characteristics Explosion-proof Explosion-proof Equipped with fully charged batteries at all times Equipped with fully charged batteries at all times Easily protected against contamination Easily protected against contamination Equipped with a remote probe for non-entry testing Equipped with a remote probe for non-entry testing Reliable, rugged, and dependable Reliable, rugged, and dependable

Operates by physically burning a small sample of the gas within the instrument. Most monitors will not report total concentration of a flammable gas. Instead, they indicate concentration as a percentage of the LEL of the gas used to calibrate the monitor. The Combustible Gas Indicator (CGI) Methane or Pentane

Lower Explosive Limit: The minimum concentration of a flammable gas in air that will ignite and burn. The Combustible Gas Indicator (CGI)

Lower Explosive Limits: Chemical NameLELUEL Ammonia15.50%27.00 % Carbon Monoxide12.50%74.20 % Methane 5.00 %15.00 % Diethy Ether 1.85 %82.00 % Proplyene 2.00 %11.10 % The Combustible Gas Indicator (CGI)

RELATIVE METER RESPONSE METHANE PENTANE XYLENE 100% 82% 75% 50% 32% 25% 0 20%40%60%80%100% Actual % LEL Meter Reading % LEL

Monitoring Oxygen Deficient Atmospheres The CGI depends on atmospheric oxygen to burn the sample within the machine. If adequate oxygen is not available, the sample will not be efficiently burned CGI may understate the actual concentration of flammable vapors or gases.

Monitor Calibration Calibrated to specific gases Must be calibrated prior to use Records of calibration should be kept with permit Bench Calibration Fresh Air Calibration

Detector Tubes ADVANTAGES Economical Minimal training required Many different types of tubes available

Detector Tubes DISADVANTAGES No continuous monitoring Poor accuracy Tubes become outdated Difficult to use in cold weather Does not detect oxygen concentration No remote monitoring

Atmospheric Monitoring Monitoring must be performed before each and every confined space entry. Procedures for safe entry into a confined space must be based on initial and ongoing air monitoring.

Atmospheric Testing ORDER OF PRIORITY FOR TESTING: 1.Oxygen deficiency / oxygen enriched 2.Flammability 3.Toxicity Direct-reading instruments are to be utilized for the following conditions in the given order of priority for testing. O²