After the initial strike on London in May 1915, zeppelins continued to hit the city with impunity, timing raids to coincide with good weather and moonless nights. Not wanting to foment panic, British civil authorities gave few air raid warnings beyond policemen on bicycles blowing whistles and shouting for people to “take cover.”
Technology also limited what Britain could do to stop the zeppelins early in the war because its airplanes were unable to soar as high as the lighter-than-air craft and machine gun fire had no effect...
... The British also began to target the zeppelins’ major vulnerability, their highly flammable hydrogen. By mid-1916, they had developed airplanes that could reach higher altitudes and fire both explosive bullets, which could tear large holes into a zeppelin’s outer skin and allow oxygen to pour into the hydrogen chambers, and incendiary bullets, which could light the volatile gaseous cocktail on fire.
-Source - History.com
The Allies only started to exploit the Zeppelin's great vulnerability to fire when a combination of Pomeroy and Brock explosive ammunition with Buckingham incendiary ammunition was used in fighter aircraft machine guns during 1916.[54]
... Zeppelins were very difficult to attack successfully at high altitude, although this also made accurate bombing impossible. Aeroplanes struggled to reach a typical altitude of 10,000 feet (
3,000 m), and firing the solid bullets usually used by aircraft Lewis guns was ineffectual: they made small holes causing inconsequential gas leaks. Britain developed new bullets, the Brock containing oxidant potassium chlorate, and the Buckingham filled with phosphorus, which reacted with the chlorate to catch fire and hence ignite the Zeppelin's hydrogen. These had become available by September 1916.[85] - Source - Wikipedia
The means of escape used by the Zepellin Captain in the movie was to jetison water ballast and any extra weight to try to rise above the effective ceiling of the planes. Obviously they could not force crew to jump out of the dirigible fast enough to gain altitude. Remember this is a partly fictional and partly historical film shot between 1927-1930 after the Great War.
Robert Mugabe is correct that with the non-incindiery bullets used pre-1916 were less than effecftive against Zepellins, even though hydrogen does burn. That is why 1930's dirigibles and WW II and later blimps switched to helium gas. The plot line ,however, does suggest that the Zepellin Captain was in fact trying to escape by rising above the ceiling of the plane by throwing out the kitchen sink and some of the crew.
I appreciate the comments. This beats playing checkers until the border opens up. But the Hindenburg crash in 1937 below shows that hydrogen was too flammable to use in airships.