Home Interviews THMG053 – Hazmat Weather with Bob Metcalfe from The Firefighter Podcast

THMG053 – Hazmat Weather with Bob Metcalfe from The Firefighter Podcast


In this episode, Bob interviews Bob Metcalfe, a meteorologist and host of The Firefighter Podcast, to discuss the impact of weather on hazmat scenes.

Complete Show Notes

1:15 Introduction to Bob Metcalfe

  • Host of The Firefighter Podcast
  • Formerly an on-air meteorologist, which can play a significant role in hazmat

2:35 Is Weather a Hazmat Response Consideration?

  • Yes! It plays just as significant of a role in hazmat as it does when responding to fires
  • There are more scientific effects of weather on hazmat than there are in firefighting

4:10 How Does Temperature Affect Hazmat?

  • Physical properties are obvious – phase changes (ice, liquid, and gas)
  • Physical states and boiling points also play an important role in response
  • Ideal gas law – pressure multiplied by volume has a direct relation to how many moles of a gas you have multiplied by a correlation and the temperature
  • Just know that when temperature goes up, there’s either an increase in pressure or volume of a gas
  • Ideal gas law also affects altitude – all of these factors change depending on where you live

10:00 Heat Index, Humidity, and Temperature

  • The heat index factors in the humidity of the air – affects evaporation of moisture from your skin
  • If the heat index is up, there’s a higher combination of heat and humidity in the air
  • Humidity refers to how much moisture is in the air – any air mass can withhold certain amounts of moisture, and 100% humidity means that parcel of air can’t hold any more moisture
  • Humidity does not equal rain, though – there must be a trigger for the rain (i.e. lifting or other trigger mechanisms)

14:30 How All of This Affects Hazmat

  • Temperature has a direct effect on the pressurization of containers and the expansion of liquids or solids
  • Humidity has a direct effect on whether things are hydrophoric and if they react with water
  • Also affects techs in terms of the physiological effects of the heat index – heat index doesn’t really affect the world around us and what we’re working with
  • Altitude also has an effect because it changes the physical and chemical properties of a lot of substances – affects boiling points, vaporization, viscosity, solubility, etc.

16:30 Wind and Hazmat

  • The Emergency Response Guidebook (ERG) has information on how far we need to evacuate depending on the wind
  • Distance of evacuation is based on whether it’s night or day – think of this as a lava lamp
  • During the day, the air close to the ground becomes hot and lighter than the air above it – this produces clouds
  • We don’t get those kinds of clouds at night because there’s no sun beating down on the ground
  • Wind goes from high pressure to low pressure – there’s more atmospheric mixing during the day and a stirring effect that creates wind
  • This isn’t a consideration at night because there’s less atmospheric mixing – as a result, there’s a larger evacuation range at night
  • Major differences between urban, suburban, and rural settings – urban heat islands often exist in cities to create their own heat and storms
  • Wind patterns are also different because large cities have buildings that form tunnels – this means the wind can’t move around as much

23:50 Which Weather Factor Has the Greatest Effect on Operators?

  • Heat index is the most important thing we should be concerned with because it can have an adverse effect on us physiologically – puts more stress on our body than anything else weather-related
  • We don’t know when we’re going to have to answer the call, which can be dangerous because we may not be prepared for the heat index

27:20 How Rain Affects Us as Hazmat Techs

  • Runoff is a concern
  • Rain also causes turbulence in the air, which can keep gasses and liquids from dispersing as much as they might otherwise

29:30 Resources That Bob M. Uses

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