Why soap liquid cannot be used for oxygen leak test ?

Why soap liquid cannot be used for oxygen leak test ? 

Soap contains animal fats  which burns easily and explosive-like in an oxygen 

Some soapy water uses surface tension to make bubbles (when there is a gas leak). Colin / Windex does not contain both so cannot be used for leak test it is used for glass and car cleaning. 

Soap water leave residues on the valve that, when they come in contact with high pressure oxygen, can ignite and cause a fire.. Remember in high pressure. if emergency to check oxygen then pressure should be low.  How? just on valve and release slightly pressure and  drop only one droplet on hose joint and after check at once wipe hose.

OR,

There are leak detector fluids sold in both welding supply and hardware stores that are safe for use with oxygen systems. It will state in bottle in detail

If you want to leak test with soapy water then first close valve  completely then test with soapy water.