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Hi.  I'm making plans to capture acoustics of some notable natural caves and temples in SE Asia.  Because of the situation, I can't be setting off pistols.  These are some huge spaces, and I'm dubious that a balloon pop will do it.  Likewise, bringing speakers for a sine sweep will be difficult.

I'm wondering if I can't use something like a big clapboard.  The issue I see is that the source is not as close to a true impulse as it is for an explosive device.  It likely has all frequencies, but not necessarily in balance.

So, my question: Can I use Deconvolver with this kind of source, to get an accurate IR?

Deconvolver may not work good with any test tones beside sine-sweeps.  You may use clapping, but it won't give you an accurate IR.

Thank you, Aleksey.  That is good to know.

Would you have any recommendations for explosive sources between a balloon pop and a gunshot?  Small firecrackers, maybe?

If you can hire a high-voltage electrical engineer you could ask them to make an electrical discharge machine (something of Nikola Tesla legacy).  I think an in-air electrical discharge is one of the best "test tones" for such tasks - it is omni-directional and you won't need to "deconvolve" it after recording.  Well, of course, it's theory - I have my doubts that such machine can be easily created for capturing big spaces.  But for smaller rooms you won't need a powerful discharge.

Gunshot and balloon pop are actually not such great sources, because their energy is concentrated in lower frequencies and the frequency response of their sound is non-linear.