Rescue from manholes (confined space) requires knowledge of gas hazards, safety gear, and rescue procedures.
confined space Rescue
Accidents due to oxygen deficiency, common in confined spaces like manholes, are broadly categorized into two types: accidents due to oxygen deficiency and hydrogen sulfide poisoning. Understanding these accidents and taking appropriate measures is crucial.
Accidents Due to Oxygen Deficiency
Cause: These occur when the oxygen concentration in the air drops. In confined spaces (such as manholes, old wells, tanks, gas pipes), poor ventilation can lead to oxygen deficiency, increasing the risk.
Measures: Checking air quality in advance, periodic ventilation during work, and carrying an oxygen concentration meter are effective.
Hydrogen Sulfide Poisoning
Cause: Hydrogen sulfide is generated during the decomposition of substances like sewage, sludge, wastewater, and pulp. It dissolves easily in water, initially irritating the eyes and nose but desensitizing them over time, posing a risk of high concentration exposure without realizing it.
Measures: Use hydrogen sulfide gas detectors, wear self-contained breathing apparatus in high-concentration gas areas, and conduct risk assessment and training before work.
In case a worker loses consciousness due to oxygen deficiency or hydrogen sulfide poisoning, it’s essential to have safety equipment and a rescue system for safely rescuing the unconscious worker from the manhole.
Rescue from Manholes (Vertical Shaft)
Rescue operations in manholes require careful handling due to gas hazards. Here are the initial actions and necessary equipment for rescue operations in manholes.
Initial Actions and Necessary Equipment
- Gas Detector: Measures the oxygen concentration and harmful gas (e.g., hydrogen sulfide) concentration inside the manhole.
- Air Breathing Apparatus: Worn by rescue team members for safety in case of harmful gases.
Rescue Procedures
- Measurement with Gas Detector:
- Wearing an air breathing apparatus, measure the oxygen concentration (must be 18% or more) and harmful gas concentration with a gas detector inside the manhole.
- Using Air Bottles:
- If gas concentrations are low, open the air bottle valve to send air into the manhole, improving the environment.
- Ventilation with Blowers:
- Use blowers for ventilation if necessary, ensuring it doesn’t hinder the activity.
- Calling the Victim:
- Call the victim by name or ask for their date of birth to check consciousness and condition using the SAMPLE principle (Symptoms, Allergies, Medication history, Past medical history, Last meal, Events leading to the incident).
- Implementing Safety Measures:
- Set up pylons to prevent falls and create a safe space for rescue operations.
- Choosing Rescue Method:
- If the victim can walk, use a ladder for rescue. For non-walking or unconscious victims, use rope rescue techniques.
Following this procedure allows effective and safe response to oxygen deficiency or gas poisoning accidents in manholes. Always prioritize team operation and safety first.
When the Rescue Vehicle Can Enter
When the rescue vehicle can enter, follow these steps:
Preparation for Rescue
- Set Up Rescue Vehicle Crane:
- At the rescue site, use the rescue vehicle’s crane to create an anchor point, establishing a safe base for lowering ropes.
- Prepare Ropes:
- Hang two ropes from the crane for rescue team members to descend safely.
Descent of Rescue Team
- Using Descent Devices:
- Rescue team members use descent devices (e.g., ID device) to safely descend using one of the ropes, controlling the descent speed.
Carrying Rescue Equipment
- Carrying Necessary Equipment:
- Carry necessary rescue equipment such as rescue slings (survivor slings or pitagores), neck collars, additional ropes, gas detectors, etc.
Rescuing the Victim
- Fitting Neck Collar and Pitagore:
- At the site, fit the victim with a neck collar and pitagore (or survivor sling) for safety during rescue.
- Guiding with Hooks and Ropes:
- Use hooks and ropes to guide and stabilize the victim, safely moving them to the rescue vehicle.
By following these steps, efficient and safe rescue operations can be performed when the rescue vehicle can enter. Always prioritize safety and the condition of the victim in rescue operations.
When the Rescue Vehicle Cannot Enter
When the rescue vehicle cannot enter, use manual devices and techniques for rescue. Here’s an easy-to-understand explanation of such rescue methods.
Preparation for Rescue
- Creating Upper Anchor Point:
- Use an Arizona Vortex or ladders to create a stable anchor point at the top of the rescue site. This anchor point serves as the base for descending and ascending ropes.
- Setting Up Ropes:
- Hang two ropes from the upper anchor point, one for the rescue team’s descent and one for supporting the rescued person.
Descent of Rescue Team
- Using Descent Devices (ID):
- Rescue team members use descent devices (ID) to safely descend using the descent rope, adjusting the descent speed for safety.
Carrying Rescue Equipment
- Carrying Necessary Equipment:
- Carry necessary rescue equipment such as rescue slings (survivor slings or pitagores), neck collars, additional ropes, gas detectors, etc.
Rescue Operations
- Creating a 4:1 Mechanical Advantage:
- Use the upper anchor point to create a 4:1 mechanical advantage (force multiplication system), making it easier and safer to lift the victim.
- Fitting Neck Collar and Pitagore:
- After descending, fit the victim with a neck collar and pitagore (or survivor sling).
- Guiding and Rescuing with Ropes:
- Guide and stabilize the victim using ropes, safely moving them to the rescue point.
Following these steps ensures effective and safe rescue operations even when the rescue vehicle cannot enter. Always prioritize teamwork and safety, and ensure proper preparation and equipment for rescue operations.
Oxygen Deficiency and Hydrogen Sulfide
Oxygen deficiency and hydrogen sulfide are dangerous situations encountered in manhole or sewer work. To work safely in these environments, the following basic knowledge is important.
Oxygen Deficiency
- Oxygen Concentration Standards: Normal atmospheric oxygen concentration is about 21%. Environments with less than 18% oxygen concentration are considered deficient and dangerous.
- Dangers: Lowered oxygen levels can cause headaches, dizziness, and breathing difficulties, and further reduction can lead to unconsciousness or death.
- Measures: Use an oxygen concentration meter to check air quality before work, ensure sufficient ventilation, or wear a self-contained breathing apparatus.
Hydrogen Sulfide
- Danger Standards: Hydrogen sulfide concentration of 10 ppm (parts per million) or more is considered dangerous. It can irritate the eyes and respiratory tract at low concentrations and cause immediate death at high concentrations.
- Pay Attention to Smell: Hydrogen sulfide smells like rotten eggs at low concentrations but becomes odorless at high concentrations, so do not rely on smell for safety.
- Measures: Use a hydrogen sulfide detector to check gas concentration, wear a gas mask or self-contained breathing apparatus as needed, and stand upwind, perform work quickly, and take other precautions.
Measurement Methods
Accurate measurement of gases like oxygen and hydrogen sulfide is crucial for protecting workers’ lives. Here’s an easy-to-understand explanation of safe gas measurement procedures.
Ensuring Safe Use of Safety Equipment
- Properly Wear Self-Contained Breathing Apparatus: Before starting work, wear a self-contained breathing apparatus correctly to avoid inhaling external air, as even one breath can be fatal.
Selecting Measurement Points
- Measure in Key Locations: In manholes or tanks, harmful gases tend to accumulate in specific spots, especially in corners or low areas, so focus measurements on these areas.
Measuring at Multiple Locations
- Measure at 5 or More Points: Conduct measurements at 5 or more different points to check air quality throughout the space, ensuring no dangerous gas accumulations are missed.
Using Measuring Instruments
- Use Oxygen and Hydrogen Sulfide Meters: Use oxygen concentration meters and hydrogen sulfide meters (or multi-gas detectors) for measurements. Ensure instruments are calibrated and accurate.
Implementing Safety Measures
- Prioritize Safety: Always prioritize safety during measurements, avoid unstable locations, and avoid working alone to minimize risks.
Consider ladder rescue for certain situations.
Reference Video
Reference page: Discover rope rescue systems, anchor types, knots, and techniques for safe and efficient low, and high-angle rescues in various terrains.
References National Fire Protection Association (NFPA)
