usually 300 feet. Long hoses are cumbersome and awkward to handle—users must take precautions to avoid kinking, snagging, or hose damage. If the hose attaches to an air pump, you must locate the pump in an area where safe, fresh air is available.
These respirators use either a hood with a clear face piece, a helmet with a clear face piece, or a strap-on half or full face piece. The hood, helmet, and full-face piece models provide eye protection. Hoods and helmets provide a continuous flow of fresh air around the entire head, whether inhaling or exhaling. Because of continuous positive air pressure, hoods and helmets do not require critical sealing around the face, so they work with beards, long sideburns, and eyeglasses. Replace the hood if it develops holes or tears. Regularly inspect the air hose, and replace it if it becomes cracked or shows wear.
Self-Contained SuppliedAir Respirator.Self-containedsuppliedairrespirators (often called a self-contained breathing apparatus—SCBA) provide clean air from pres- surized tanks that a user carries on their body, similar to a scuba diver. The tank con- nects to either a half- or full-face piece. Full-face piece models provide eye protection.
Self-contained units provide a limited quantity of air. Once you exhaust the air supply, the system cannot provide any protection. To conserve the air supply, a pres- sure demand regulator admits fresh air into the mask as you begin to inhale. Airflow diminishes when you exhale. Manufacturers equip these units with warning devices to alert users when the air supply is getting low. Air tanks may be heavy and bulky, but they allow unlimited mobility.
Cleaning and maintaining a self-contained supplied air respirator is critical to its safe operation. The mask must fit properly to seal against the face. Exhalation valves have to be in good working order to prevent any outside air from enter- ing. Regularly inspect the air hose, and replace it if it becomes cracked or shows wear. Keep pressure regulators clean, dry, and protected from damage.
Never enter an enclosed fumigated area, even after vent- ing, without measuring for toxic levels of fumigant vapors. Several different atmosphere-monitoring devices detect and measure vapors. Depending on the type of monitoring device you use, you may need to wear required respirators and protective clothing when taking air samples. Some monitoring equipment may allow remote sensing. Take measurements in several loca- tions within a confined space, since localized pockets in the area sometimes trap vapors.
Choose atmosphere-monitoring equipment that is capable of measuring SO2 levels. Various manufacturers produce air samplers that use detector tubes for SO2 gas. These inexpensive samplers have a small hand pump or syringe device to pull air from the atmosphere into the de- tector tube. You must wear a supplied air respirator when taking air samples with these types of monitoring devices. Be certain that the monitoring device provides accu- rate readings at least in the range of 0.5 to 4.0 ppm SO2. Learn about the shortcomings of these devices, since other contaminants in the atmosphere can produce erroneous readings. Get proper training on this equipment so you can reliably detect when the SO2 level exceeds 2.0 ppm. Examples of SO2 detectors include those manufactured by Draeger, Kitagawa, and Sensidyne, using the correct air samplers with the appropriate detectors.