Occupational Hazards

Question 1

Define boilover?

Answer 1

• Boil over takes many hours to occur.
• A layer of water is located at bottom of tank mixed with sludge and waste.
• When the thermal layer (travelling at 0.3m to 1m an hour) reaches the bottom of the tank, the water is instantly vaporised (water to steam ratio of 1700:1).
• This causes a piston effect which violently forces unburnt product up through the fire.

Question 2

Define slopover?

Answer 2

• Pockets of water interspersed within crude oil are heated to boiling point and expand to steam.
• The force of this expansion causes frothing of the top layers of the product which can then flow down the sides of the tank and into the bunded area.

Question 3

What is a bund?

Answer 3

• Bunds are walls surrounding flammable liquid tanks and are designed to contain the spill should a leak occur.
• They are designed to hold 100% of tank’s contents, or the contents of the largest tank in the bund.
• Constructed of concrete or earth.

Question 4

Define SPDRA?

Answer 4

Safe
Person
Dynamic
Risk
Assessment

Question 5

How do FFs determine risk rating?

Answer 5

Likelihood vs Consequence = Risk Rating

Consequences = Catastrophic, Major, Moderate, Insignificant

Likelihood = Certain, Very Likely, Likely, Rare

Risk Rating =
* Extreme - Do not proceed. Alternate tactics required.
* High - Proceed only where significant benefit.
* Medium - Normal procedures should suffice and monitor for escalation.
* Low - Normal procedures should suffice.

Question 6

What is a BLEVE?

Answer 6

Boiling
Liquid
Expanding
Vapour
Explosion

Question 7

What are differences between LPG & Natural Gas?

Answer 7

LPG:
* Proprane & Butane
* Low boiling point
* Vapor Density: 1.5
* LEL 1.5%
* UEL 10%

Natural Gas:
* Colourless and odourless (odorant added)
* Predominately Methane (85% to 95%)
* Vapor Density .55
* LEL 5%
* UEL 15%

Question 8

Define the acronym DEBRiS?

Answer 8

Decontamination
Entry & Exit of Hot Zones
BA Service Area
Rehab/AV monitoring
incident accountability of all personnel
Staging Area

Question 9

Why do FRV use DEBRiS? (3)

Answer 9

1. It enhances firefighter safety
2. It enhances accountability
3. It allows for scalability

Question 10

What are the safe working practices for working in high expansion foam?

Answer 10

1. BA must beworn
2. Toxic gases may be trapped in high expansion foam
3. Visibility is nil and hearing may be impaired
4. Guidelines must be used
5. Strict supervision must be maintained over persons entering foam