30 Questions
What is the purpose of determining the combined TLV?
To determine if the mixture exceeds the threshold limit value
What is the unit of measurement for airborne particulate concentrations?
Milligrams per cubic metre of air
What is the IDLH condition?
A condition that poses immediate danger to life or health
What is the purpose of the pH scale?
To measure a substance's acidity or alkalinity
What is the significance of a pH below 7?
The substance is acidic
What is the Lower Explosive Limit?
The minimum concentration of a gas or vapour that will ignite
What should you do if a fallen wire lies across a vehicle with occupants?
Instruct the occupants to stay where they are until electrical crews arrive
Why is it important to clear the vehicle of any pools of water?
To prevent the water from being energized by the live wire
What should the operator do if they are injured and cannot move the vehicle?
Stay in the vehicle until electrical crews arrive
What is a major hazard for crane operators?
Contact with overhead power lines
Why is it important for responders to know about the electrical systems used by welders?
To be aware of the electrical hazards and take positive steps to eliminate and/or mitigate those hazards
What can happen if a haul truck comes into contact with a power line?
The tires may explode
What is the typical temperature range for mild hypothermia?
37.2°C - 36.1°C
At what temperature does violent shivering persist in hypothermia?
33.9°C - 32.2°C
What is the primary area of heat loss in the body?
Head and neck
At what temperature does shivering typically stop in hypothermia?
32.2°C - 30.0°C
What is a sign of moderate hypothermia?
Gross muscle movements sluggish
What is a consequence of severe hypothermia?
All of the above
What can happen to tires of a vehicle that contacts overhead power lines?
They may start burning inside
Why should rescue teams approach a vehicle that contacted power lines with caution?
To avoid injury from flying debris
What is a hazard that operators of equipment used during trenching and excavation activities should be aware of?
Buried power and communication lines
What should mine rescue teams ensure before conducting rescue operations?
That energy isolation is complete
What should responders do when arriving at the incident scene?
Stage response vehicles at a distance that avoids exposure to electrical hazards
What should be used when working near energy sources?
Lock-out/tag-out devices
What is the primary reason acetylene is dissolved in acetone in its cylinders?
To allow for safe storage and transportation at higher pressures
What is the effect of high temperatures with low humidity on the human body?
It is not dangerous except from the blistering effect of heat
What is the minimum oxygen level below which non-toxic gaseous impurities become dangerous?
19.5%
What is the temperature of the flame produced by acetylene when combined with oxygen in the oxyacetylene process?
3,260 C/5,900 F
What is the range of concentrations within which acetylene can be explosive?
2.8%–81%
What is the hazardous compound that can be formed when acetylene comes into contact with copper or copper alloys?
An explosive compound
Study Notes
Calculating TLV (Threshold Limit Value)
- The equation for determining the combined TLV is: C1/T1 + C2/T2 + … + Cn/Tn = Dose
- Where C is the concentration and T is the threshold limit value
- If Dose is greater than 1, the TLV for the mixture has been exceeded
Toxicology
- Median Lethal Dose (LD50) refers to the dose of a toxic substance that would be fatal for 50% of a test population
- Median Lethal Concentration (LC50) refers to the concentration of a toxic substance that would be fatal for 50% of a test population in an atmosphere
- Immediately Dangerous to Life and Health (IDLH) refers to a condition posing immediate danger to life or health, or a condition posing an immediate threat of severe exposure to contaminants
Measuring Concentrations
- Airborne particulate concentrations are measured in milligrams per cubic meter of air (mg/m3)
- Gaseous concentrations are measured as parts per million or % by volume
- Lower and Upper Explosive Limits refer to the minimum and maximum concentrations of a gas or vapour in air that will ignite when exposed to an ignition source
- Relative density (vapour density or specific gravity) is the ratio of the density of a substance to the density of a standard substance under specified conditions
pH Scale
- The pH scale is a means of measuring a substance’s acidity or alkalinity
- Pure water has a pH of 7
- A pH below 7 indicates that a substance is acidic, while a pH above 7 indicates that a substance is basic or alkaline
Electrical Hazards
- Direct contact with power lines is not necessary to pose an arcing hazard as power can arc from the lines to a crane or other piece of equipment
- Workgroups such as welders, crane operators, and haul truck operators should be aware of electrical hazards and take positive steps to eliminate and/or mitigate those hazards
Hypothermia
- Mild Hypothermia: 37.2°C – 36.1°C, cold sensation, goose bumps, unable to perform complex tasks with hands
- Moderate Hypothermia: 35.0°C – 33.9°C, shivering, intense, lack of muscle coordination becomes apparent
- Severe Hypothermia: 32.2°C – 30.0°C, muscle rigidity, semiconscious, stupor, loss of awareness of others
- Bodily heat loss is critical in the head and neck areas
Heavy Equipment Operations
- Contact with overhead power lines is a major cause of fatalities in the industry
- Electricity can travel from a power line to a worker touching any part of the crane or the load
- Tires can explode during or after contact with power lines, causing a build-up of gases and heat which could cause the tire to explode later
Electrical Emergencies
- Always assume that all electrical wires and equipment are energized until proven otherwise
- Mine rescue teams must ensure that energy isolation is complete prior to conducting rescue operations
- Stage response vehicles at a distance that avoids exposure to electrical hazards
- Control the incident scene to eliminate unauthorized access and prevent exposure to electrical hazards
Impure Air
- Non-toxic gaseous impurities are not dangerous unless they have displaced oxygen to a level below 19.5%
- Some toxic gases have deadly effects, even in very low concentrations
Acetylene Gas
- Acetylene is a colourless, highly flammable hydrocarbon fuel
- Acetylene produces industry’s hottest flame (3,260°C/5,900°F) when combined with oxygen in the oxyacetylene process
- Acetylene is very unstable and can become dangerously explosive if compressed above 100 kPa (15 psi) in the free state
- Acetylene has an explosive range of 2.8%–81%
- Can displace oxygen and is formed by mixing water with calcium carbide
This quiz covers the calculation of combined Threshold Limit Values (TLV) and Median Lethal Dose (LD50) in toxicology. Learn about the equations and concepts used to determine the toxicity of substances.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
