39 Questions
What does one part per million (ppm) represent in terms of distance?
1 metre in 1,000 kilometres
What is the purpose of Threshold Limit Values (TLVs)?
To establish a safe concentration of substances for most workers
What is the time period for which the TLV-TWA is calculated?
A normal 8-hour workday
What is the percentage of people who may experience discomfort from some substances at concentrations at or below the threshold limit?
A small percentage
What is the volume of liquid in which 1 millilitre is equivalent to 1 ppm?
1,000 litres
What is the area of the square in which 1 square centimetre is equivalent to 1 ppm?
100 square metres
When is the 8-hour TLV referred to?
When TWA is not indicated
What should you do when dealing with a serious ammonia leak or spill?
Use a water spray or fog to reduce the gas cloud
What type of extinguishers are suitable for fighting fires involving ammonia?
Carbon dioxide and powder extinguishers
What should you do with ammonia cylinders in a fire?
Move them away from the fire area if it is safe to do so
What happens when pressurized ammonia containers are exposed to fire?
They rupture and release ammonia gas
What is the minimum concentration of ammonia in the air that can cause moderate irritation of mucus membranes?
5–15 PPM
What is the characteristic of ammonia gas that makes it harder to extinguish fires?
It is not readily ignited
What is the maximum concentration of ammonia in the air that can be fatal in 30 minutes?
400 PPM
What is the characteristic of carbon dioxide gas?
It is a colourless, odourless gas
What is the primary consideration when dealing with two or more hazardous substances that have a similar toxicological effect on the same target or system?
The combined effect of the substances
What is the significance of a dose greater than 1 in the equation for determining the combined TLV?
The TLV for the mixture has been exceeded
What is the Median Lethal Dose (LD 50) a measure of?
The dose of a toxic substance that is fatal for 50% of a test population
What is the purpose of the Threshold Limit Value – Ceiling (TLV‑C)?
To determine the concentration of a toxic substance that should not be exceeded during any part of the working exposure
What is the Median Lethal Concentration (LC 50) a measure of?
The concentration of a toxic substance that is fatal for 50% of a test population
What is Immediately Dangerous to Life and Health (IDLH)?
A condition posing an immediate threat to life or health
What is the equation for determining the combined TLV?
𝐶1 𝐶2 𝐶𝑛 + +⋯ = 𝐷𝑜𝑠𝑒 𝑇1 𝑇2 𝑇𝑛
What is the significance of the Threshold Limit Value (TLV)?
It is the concentration of a toxic substance that should not be exceeded during any part of the working exposure
What is the minimum percentage of oxygen that should be present in the atmosphere at a workplace?
19.5%
What is cross sensitivity in gas detection equipment?
The response of a sensor to a gas that is not the target of the sensor
What is the effect of oxygen deficiency at 15% O₂ in the atmosphere?
Dizziness, buzzing noise, rapid pulse, headache, blurred vision
What is the response time of a gas detection instrument?
The ability to react to its specific gas in the time specified
What is the chemical symbol for propane?
C₃H₈
What is the limit of detection (LOD) of a gas detection instrument?
The lowest quantity or concentration of a substance that the instrument can register within a margin of confidence
What is precision in gas detection?
The degree to which repeated measurements under unchanged conditions show the same results
What is the primary hazard of propane vapour?
It is heavier than air and can accumulate in low places
What is the explosive range of propane?
2.4%–9.5%
What is noise or drift in gas detection?
How much readings fluctuate when the quantity or concentration of a substance stays the same
What is dynamic range in gas detection?
The ratio between the largest and smallest possible signals
What happens when liquid propane is converted to vapour?
It will expand to about 270 times its liquid volume
What is the primary effect of propane on humans?
It can cause an oxygen-deficient atmosphere resulting in asphyxiation
What is a common interference in gas detection equipment?
All of the above
Why is propane commercially scented?
To detect leaks or escaping gas
What is important to follow when using gas detection equipment?
The manufacturer's specifications for application and use
Get familiar with the concepts of toxic chemicals, concentrations, and metric units. Learn to visualize and understand the scale of toxic gases, including parts per million (ppm) and its equivalent representations. Improve your knowledge of environmental science and chemistry.
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