What Is The #1 Cause Of Confined Space Fatalities?
Oxygen deficiency is still the leading cause of death in Confined Space incidents.
The concentration of oxygen in normal air is approximately 20.9%. The balance (over 78%) consists primarily of nitrogen. The remaining fraction includes small amounts of water vapor, carbon dioxide and argon, as well as traces of other gases.
OSHA 29 CFR 1910.146, “Permit Required Confined Spaces”, contains the requirements for practices and procedures to protect employees in general industry from the hazards of entry into permit-required confined spaces. The OSHA standard defines an oxygen deficient atmosphere as any atmosphere containing less than 19.5% oxygen by volume. Any atmosphere that contains less than 19.5% oxygen is hazardous, and may not be entered by unprotected workers.
Any oxygen concentration other than 20.9% indicates an abnormal condition. A less than normal concentration of oxygen by definition indicates a greater than normal concentration of some other component or the presence of a contaminant in the atmosphere being sampled. Even when the oxygen concentration does not constitute a statutory hazardous condition, workers should determine the cause of the abnormal reading prior to entering a confined space. The safest approach is to initiate entry only when monitoring has determined that a “fresh air” oxygen concentration of 20.9% exists in the space.
How do I Pick the Best Gas Detector for Use in a Confined Space?
The “best” Confined Space Gas Detector does not come from any one manufacturer. It is the instrument that best fulfills the requirements for your operational application(s). Price must not be the sole consideration, as many features of the instrument should be determined:
Sensor Selection – Does the instrument offer the selection of sensors needed for the known and potential atmospheric hazards associated with the confined spaces to be monitored?
Diffusion or Sample-Draw Method – Determine the best function of gas detecting for your application. Diffusion instruments utilize natural air currents to bring the atmosphere being sampled to the instrument. They are often preferred for work area monitoring. Sample-Draw kits enable diffusion-type instruments to sample from remote locations. This is useful for below ground stratification of gases tested such as down a manhole or utility vault.
Classification for Intrinsic Safety – Instruments purchased for use in a confined space, hazardous location, or other environment characterized by the potential presence of flammable or explosive gases, should carry a Classification of Intrinsic Safety.
Durability – Is the instrument durable enough to take the abuse it is likely to receive in the application? How well is it protected from the effects of radio frequency interference (RFI) and electromagnetic interference (EFI)? Consideration should be given to the effects of high and low temperatures on the design, and resistance to water and dust.
Source of Power – Instruments today are powered with Alkaline batteries, rechargeable battery packs, or both. Considering the pros and cons of each should be a consideration.
Alarms – The majority of new detectors offer three types of alarm function; audible, visual and vibratory. Alarms should be loud, highly visible and sufficient to grab the attention of the instrument user.
Consideration of the package of included accessories, instrument warranty, calibration frequency, available technical service and overall operability of the instrument being evaluated will help ensure a suitable product selection. Note: Many manufacturers offer a “field evaluation” period prior to purchase… there is no substitute for hands-on experience!
If I Calibrate My Instrument With Pentane, Will It Sense Methane As Well?
The Catalytic Bead (LEL) sensor can degrade due to “poisoning” and if so, the sensitivity tends to be lost first with regards to Methane. A partially poisoned sensor might still respond accurately to Pentane, while showing a dangerously reduced response to Methane. Some manufacturers offer an “equivalent” mixture of calibration gas (Methane) to address this condition. Contact the instrument manufacturer for specific information and guidance on the potential effects to their technology.