4 ms·

http://www.firefightermath.org/index.php?option=com_content&view=article&id=29&Itemid=43 http://www.firefightermath.org/index.php?option=com_content&... "A 100

http://www.firefightermath.org/index.php?option=com_content&view=article&id=29&Itemid=43 http://www.firefightermath.org/index.php?option=com_content&... "A 100-foot length of 1-inch diameter hose is charged with water. How many gallons of water are in that length of hose?" Ugh.

knz 9y ago
The section on unit conversions (http://www.firefightermath.org/index.php?option=com_content&view=article&id=23&Itemid=125 http://www.firefightermath.org/index.php?option=com_content&...) just makes me wonder why fire fighters don't use metric... "How many pints are in a 5-gallon pail? How many cups are in a 5-gallon pail?"
- ateesdalejr 9y ago
  Probably because most firefighters were taught and grown up on the imperial system of measurement...
  - yardie 9y ago
    If they were taught in a US school for the last 40 years they were taught metric. If they were enlisted at any point in the last 30 years they were taught, and used, metric. If they can't handle the metric system then they probably aren't that good at math and are just using rote memorizations.
- brooksgarrett 9y ago
  Speaking from experience, it's primarily due to 'tradition.' All of your combi-nozzles and rate control valves are rated and marked in GPM (Gallons per minute) and hose is purchased and stored as 50' sections. NFPA specifications for the hose required on a first due engine are in feet. A department can't decide to use metric alone. The entire industry first would need to support at the minimum both standards.
  - johansch 9y ago
    It's probably possible, somehow, to quantify how many americans perish every year because of this.
    - maxerickson 9y ago
      I bet it is close to 0. In recent years, the total number of fire deaths is 3000 to 4000 per year: https://www.usfa.fema.gov/data/statistics/fire_death_rates.html https://www.usfa.fema.gov/data/statistics/fire_death_rates.h... Many of those deaths will have happened regardless of the response. In some sense, across 300 million people, even 3000 is close enough to zero (there's more than 2.5 million total deaths each year in the US). That doesn't mean that improving fire response isn't important, but it might not be a very good place to look for incremental improvements in mortality.
      - brooksgarrett 9y ago
        I agree. I've never been on a fireground and had someone yell, "We lost the house because you didn't divide by 12!" Fireground math is a very rough science. Every engine in our district has pre calculated charts for every cross lay and discharge so you aren't doing the math on scene. Additionally, once you deploy line you have a radio and can ask the engineer to increase or decrease pressure with no math required. A much bigger issue is the lack of recruitment and volunteerism in the American fire service. People simultaneously don't want to increase property taxes to fund career departments and they also don't want to volunteer. Communities can't have it both ways. Lack of staffing is a far greater risk than whether I'm dividing by 10 or 12.
    - mindcrime 9y ago
      I agree with @maxerickson, I'd bet that that number is approximately 0. The reasons people perish from fires rarely if ever have anything to do with a math mistake on something like this.
firethief 9y ago
It's not that bad if you don't need an exact answer. Just convert to metric, multiply it out, and convert back.
- johansch 9y ago
  That is.. bad, particularly since the presumed context here is about fire emergencies where speed is of the essence. Any extra steps will add delays and/or opportunities for potentially disastrous mistakes. https://motherboard.vice.com/en_us/article/qkvzb5/the-time-nasa-lost-a-mars-orbiter-because-of-a-metric-system-mixup https://motherboard.vice.com/en_us/article/qkvzb5/the-time-n...
  - Scoundreller 9y ago
    It’s not as bad as you make it sound. The original problem requires plenty of conversions (to cubic inches) and memorization of infrequently used constants (how many cubic inches in a gallon?). If imperial isn’t your thing, doing it in metric is easier, at least it was for me.
jcranmer 9y ago
"A 100m length of 1cm hose is charged with water. How many liters (1 dm³) of water are in that length of hose?" That problem is still no fun to do in your head. If it's important to do frequently, it's not hard to memorize the constant for "1 ft of 1 in-diameter hose = X gallons" and then multiply as appropriate.
- ak217 9y ago
  Actually, it's trivial to do in your head. 100 * 100 cubic centimeters of water = 10 liters. Times pi/4 to correct for the circular cross section, so approx. 8 liters.
mindcrime 9y ago
Don't worry, to a first approximation we can say that no firefighter on a fireground has ever had to make that calculation. It's semi-handy to know in terms of things like this: 5" supply hose holds about a gallon per foot of water when charged, and water weighs just a little more than 8 lbs per gallon, so a charged 100' section of 5" supply hose weighs over 800 lbs. So make sure you have the hose where you want it before charging it, because it's damn hard to move afterwards and the like. In terms of doing math on the fireground, at least in a structural fire scenario (wildland firefighting has some other concerns) the single biggest one is usually flow-rate. That is, a crew has stretched a 200' pre-connected 2" attack line, and wants to go in flowing 200 gpm to attack the fire. As the engineer, what pressure do you configure on that discharge to give them their 200 gpm? Here's the kicker though... almost nobody sits there thinking "Well, the friction loss per foot of 2" hose at 200 gpm is x, multiply x by 200, assume a desired pressure of 100 psi at the nozzle, blah, blah, blah.". No, instead somebody precomputed the common configurations, wrote them on an index card, laminated it, and taped it to the pump panel. Plus the engineer probably has the really common ones memorized anyway, and/or has figured out a heuristic that's "good enough".

knz 9y ago

The section on unit conversions (http://www.firefightermath.org/index.php?option=com_content&view=article&id=23&Itemid=125 http://www.firefightermath.org/index.php?option=com_content&...) just makes me wonder why fire fighters don't use metric... "How many pints are in a 5-gallon pail? How many cups are in a 5-gallon pail?"

ateesdalejr 9y ago
Probably because most firefighters were taught and grown up on the imperial system of measurement...
- yardie 9y ago
  If they were taught in a US school for the last 40 years they were taught metric. If they were enlisted at any point in the last 30 years they were taught, and used, metric. If they can't handle the metric system then they probably aren't that good at math and are just using rote memorizations.
brooksgarrett 9y ago
Speaking from experience, it's primarily due to 'tradition.' All of your combi-nozzles and rate control valves are rated and marked in GPM (Gallons per minute) and hose is purchased and stored as 50' sections. NFPA specifications for the hose required on a first due engine are in feet. A department can't decide to use metric alone. The entire industry first would need to support at the minimum both standards.
- johansch 9y ago
  It's probably possible, somehow, to quantify how many americans perish every year because of this.
  - maxerickson 9y ago
    I bet it is close to 0. In recent years, the total number of fire deaths is 3000 to 4000 per year: https://www.usfa.fema.gov/data/statistics/fire_death_rates.html https://www.usfa.fema.gov/data/statistics/fire_death_rates.h... Many of those deaths will have happened regardless of the response. In some sense, across 300 million people, even 3000 is close enough to zero (there's more than 2.5 million total deaths each year in the US). That doesn't mean that improving fire response isn't important, but it might not be a very good place to look for incremental improvements in mortality.
    - brooksgarrett 9y ago
      I agree. I've never been on a fireground and had someone yell, "We lost the house because you didn't divide by 12!" Fireground math is a very rough science. Every engine in our district has pre calculated charts for every cross lay and discharge so you aren't doing the math on scene. Additionally, once you deploy line you have a radio and can ask the engineer to increase or decrease pressure with no math required. A much bigger issue is the lack of recruitment and volunteerism in the American fire service. People simultaneously don't want to increase property taxes to fund career departments and they also don't want to volunteer. Communities can't have it both ways. Lack of staffing is a far greater risk than whether I'm dividing by 10 or 12.
  - mindcrime 9y ago
    I agree with @maxerickson, I'd bet that that number is approximately 0. The reasons people perish from fires rarely if ever have anything to do with a math mistake on something like this.

firethief 9y ago

It's not that bad if you don't need an exact answer. Just convert to metric, multiply it out, and convert back.

johansch 9y ago
That is.. bad, particularly since the presumed context here is about fire emergencies where speed is of the essence. Any extra steps will add delays and/or opportunities for potentially disastrous mistakes. https://motherboard.vice.com/en_us/article/qkvzb5/the-time-nasa-lost-a-mars-orbiter-because-of-a-metric-system-mixup https://motherboard.vice.com/en_us/article/qkvzb5/the-time-n...
- Scoundreller 9y ago
  It’s not as bad as you make it sound. The original problem requires plenty of conversions (to cubic inches) and memorization of infrequently used constants (how many cubic inches in a gallon?). If imperial isn’t your thing, doing it in metric is easier, at least it was for me.

jcranmer 9y ago

"A 100m length of 1cm hose is charged with water. How many liters (1 dm³) of water are in that length of hose?" That problem is still no fun to do in your head. If it's important to do frequently, it's not hard to memorize the constant for "1 ft of 1 in-diameter hose = X gallons" and then multiply as appropriate.

ak217 9y ago
Actually, it's trivial to do in your head. 100 * 100 cubic centimeters of water = 10 liters. Times pi/4 to correct for the circular cross section, so approx. 8 liters.

mindcrime 9y ago

Don't worry, to a first approximation we can say that no firefighter on a fireground has ever had to make that calculation. It's semi-handy to know in terms of things like this: 5" supply hose holds about a gallon per foot of water when charged, and water weighs just a little more than 8 lbs per gallon, so a charged 100' section of 5" supply hose weighs over 800 lbs. So make sure you have the hose where you want it before charging it, because it's damn hard to move afterwards and the like. In terms of doing math on the fireground, at least in a structural fire scenario (wildland firefighting has some other concerns) the single biggest one is usually flow-rate. That is, a crew has stretched a 200' pre-connected 2" attack line, and wants to go in flowing 200 gpm to attack the fire. As the engineer, what pressure do you configure on that discharge to give them their 200 gpm? Here's the kicker though... almost nobody sits there thinking "Well, the friction loss per foot of 2" hose at 200 gpm is x, multiply x by 200, assume a desired pressure of 100 psi at the nozzle, blah, blah, blah.". No, instead somebody precomputed the common configurations, wrote them on an index card, laminated it, and taped it to the pump panel. Plus the engineer probably has the really common ones memorized anyway, and/or has figured out a heuristic that's "good enough".