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A quiz for everyone

Tim McElwain
Tim McElwain Member Posts: 4,608
What are the upper and lower explosive limits of Natural Gas?

What are the upper and lower explosive limits of Propane?

What is the ignition temperature of Natural Gas?

What is the ignition temperature of Propane?

Specific Gravity of Propane  -  Natural Gas?

What should you do when you open a basement door and smell gas?


  • Tim McElwain
    Tim McElwain Member Posts: 4,608
    Have fun

  • Devan
    Devan Member Posts: 138

    5% to 15% NG

    2% to 10% Propane

    @ 1100 *F NG

    @850 * F Propane

    Not sure of the specifics, but I know propane is heavier than air, therefore greater than 1, and NG lighter than air therefore less than 1.
  • Thanks Tim,,,,,

    but I`ll wager the "MIGHTY EATHERTON" knows!!,,,, as always. 
  • Timco
    Timco Member Posts: 3,040
    specific gravity

    At my altitude or yours? I'll bet the BTU's per cubic foot vary from here to these as well...

    Just a guy running some pipes.
  • MikeyB
    MikeyB Member Posts: 696

    Upper & Lower limits of N.G = 14% & 4%

    Upper & Lower limits of Propane= 9.5% & 2.1%

    Ignition of NG= 1100-1200 degrees

    Ignition of Propane= 920-1020 degrees

    S.G of NG= .64

    S.G of propane= 1.53

    Evacuate the premise and call 911
  • MikeyB
    MikeyB Member Posts: 696
    edited February 2010

  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,487

    are you having another bad day? 
    Retired and loving it.
  • TonyS
    TonyS Member Posts: 849
    Call 911

    I once owned a company called safegas. I designed a system that automatically turned off the gas in the event of a gas leak. After years of dealing with UL and gas companies, one of the major sticking points was in the directions of who to call in the event of a gas leak. We said the same thing, call 911. Needless to say that didn't go over well with the Gas companies. They want you to call them, the gas company, because that 911 thing becomes public information and cant be buried. Needless to say the company failed because we had overlooked the simple fact that people in general wouldnt spend  15 dollars on a smoke detector if it wasn't mandatory, they were never going to spend 2000.00 on a gas shutoff system.
  • bob_46
    bob_46 Member Posts: 813
    More Quiz

    At what pipe size does the National Fuel Gas Code require displacing the air in the line

    with an inert gas before allowing natural gas to enter the pipe?
  • Jamie Hall
    Jamie Hall Member Posts: 22,877
    May I add...

    to call 911 and evacuate?  Don't turn any switches on or off; leave them be.  And evacuate to a considerable distance and then use your cell or a neighbour's phone to make the call.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MikeyB
    MikeyB Member Posts: 696

    I agree Jamie
  • Jim Bennett
    Jim Bennett Member Posts: 607
    I believe.....

    it's 3 inch, but will have to check.

    Is there any information about the Conn. power plant explosion? My first though was purging without inert gas.

    Jim Bennett
  • joe_94
    joe_94 Member Posts: 39
    Break windows?

    You smell  a lot of gas.

    You get out.

    Is there any liklihood you can save the house by throwing rocks through the windows to vent the place?

    I have always wondered that, but in reality am not an accurate pitcher nor do we keep rocks around.
  • Tim McElwain
    Tim McElwain Member Posts: 4,608
    It is a good idea to be aware

    of the danger of smelling gas because the nose doesn't know what percentage of gas is in an area.

    The lower explosive limit for Natural Gas is 4.5% and the upper is 14.5%. propane is 2.1% lower and upper is 9.5%. Ignition temperature of Nat Gas is 1100 to 1200° F and propane 920°F.

    When you smell gas and do not know the source or the level then evacuate the premises and call first responders. Typically the Fire Dept have testers and also the local gas company.

    If you have a tester then proceed as follows, as long as the level remains below 2% (covers both propane and natural gas as you have really no idea which it may be) you may enter and when doing so "VENTILATE" THE AREA OPENING WINDOWS AND DOORS. The minute the level exceeds 2% "EVACUATE".

    Most explosions are caused by low levels of either fuel in the LEL level. They cause less damage and typically do not have a fire following. Upper levels of gas natural or propane are much more destructive. The maximum explosion takes place with natural gas at 10% gas 90% air what is called the optimum burning speed, this causes the greatest damage. The same with 4.5% propane. UEL explosions are typically then gas fed fires.

    The number one cause of gas explosions are related to damage done by contractors digging around gas piping. Very little is attributed to mechanical failure or corrosion. An even lower number caused by failure of appliances.

    No one should ever enter any building that has an odor of gas unless you have a tester and are trained in how to use it.

    I have been involved in a number of gas investigations involving gas explosions and I can tell you they are really never the same. You learn something new every time.

    I also have experienced first hand twice an explosion occurring upon my arrival to investigate a smell of gas. In one of those I was approaching the building when it blew, I was 25 feet away from the building when it blew and the blast picked me up and deposited me about 15 feet away. You gain a very healthy respect for this stuff.

    Propane is even more dangerous because its specific gravity 1.52 is heavier than air and it tends to gather in lower areas. Natural gas at around .6 for SG is lighter than air and tends to rise and dissipate

    While we are discussing this Carbon Monoxide is also in addition to being colorless, odorless and unable to be sensed with the human senses is very explosive. Explosive limits 12.5% to 74%.
  • Tim McElwain
    Tim McElwain Member Posts: 4,608
    edited February 2010
    i believe it is 3"

    but the gas company I worked for did 2" and above and we typically used nitrogen or in some isolated cases carbon dioxide. All purging really should be done to outdoors in a very well ventilated area. Frequent tests should be done of the vented gases for actual measurement. Do not rely on the odorant as it is known to be faded by new piping installation especially with a long run of such piping.
  • TonyS
    TonyS Member Posts: 849
    Gas detectors

    are readily available and inexpensive. Mount low for LP and high for natural.
  • REX
    REX Member Posts: 29
    grand puba sez

    gas make big bom....bad,fire HOT! unless inside a heating,water heating,or engine application sez fire marchall REX.
This discussion has been closed.