Final answer:
Turbulent smoke indicates a flashover environment and potential ignition, while laminar smoke flow shows the system is still absorbing heat. Firefighters use the observation of smoke flow to assess potential hazards in fire situations. The correct completion of the statement is 'Turbulent smoke' and 'Smoke leaving.'
Step-by-step explanation:
The most important smoke observation is whether its velocity is turbulent or laminar. Turbulent smoke is ready to ignite and indicates a flashover environment that may be delayed by improper air mix (ventilation limited). Smoke leaving a building doesn't mean safe; it only means that the box is still absorbing heat. The proper fill in the blanks for the statement would be: Turbulent, Smoke leaving.
When smoke rises, it initially has a smooth flow, known as laminar flow. It transitions into swirls and eddies as it becomes turbulent. Observing smoke flow can tell firefighters about potential hazards, such as the risk of flashover, which is a near-simultaneous ignition of most of the combustible materials in an enclosed area.
Laminar flow indicates lower energy and less resistance, whereas turbulence indicates higher energy and more resistance, with layers mixing and significant velocities in various directions.