here's a DoD instruction for implenting CRSC.
https://www.hrc.army.mil/site/crsc/documents/CRSC2_Guidance.pdf
Direct Result of Armed Conflict - The disability is a disease or injury incurred in the
line of duty as a direct result of armed conflict. The fact that a member incurred the
disability during a period of war or an area of armed conflict or while participating in
combat operations is not sufficient to support a combat-related determination. There
must be a definite causal relationship between the armed conflict and the resulting
disability.
Armed conflict includes a war, expedition, occupation of an area or territory, battle,
skirmish, raid, invasion, rebellion, insurrection, guerilla action, riot, or any other action in
which Service members are engaged with a hostile or belligerent nation, faction, force, or
terrorists.
Armed conflict may also include such situations as incidents involving a member while
interned as a prisoner of war or while detained against his or her will in custody of a
hostile or belligerent force or while escaping or attempting to escape from such
confinement, prisoner of war, or detained status.
So, incoming fire would be engagement with the enemy, in my view. I think there is some wiggle room for the services to disagree with that, and there is questions about how close the incoming fire was to you. If as part of that engagement you had to seek cover and were injured, I think there is an argument for combat related. There is no requirement for your life to be in danger, doesn't play in. If there is shrapnel from the indirect fire, that helps make it pretty clearly armed conflict I think. Now, I could see that you might draw a relationship between burn pits only found in the armed conflict and a resulting disability, but it seems harder, after all, burning trash isn't unique to war. Ultimately there is room for the services to make judgement calls on how all this is interpreted, you just have to make the case as clear as possible for them.
You could consider the other criteria, but those don't seem to apply. Maybe you could argue the bunker or burn pits where instrumentality of war... maybe the bunker... maybe.
b. While engaged in hazardous service,
c. In the performance of duty under conditions simulating war, or
d. Through an instrumentality of war.
Now, it does talk about presumptive conditions for the gulf war region are also presumptive for combat related. If you can get the VA to mark the asthma as presumptive because of gulf war service (its not on the list, but they may be more willing to accept air quality and presumptive better than the CRSC folks), then the service has to come back with evidence that it isn't combat related. I have heard of people applying for CRSC based off chronic fatique or IBS, which are listed as presumptive and being turned down. No idea how they presented their argument though. Also, since its service connected asthma, does it even fall under the presumptive rule as stated?
Ultimately, applying is a good idea. Having your case make sense, as far as possible, is also a good idea though. Make sure your argument matches up to the program's criteria, don't assume they will draw the right connection.
Now, this is all assuming you don't need the combat related for the 199, i.e. for non-taxed seperation pay. If that's the case you do need to present these arguments to the PEB instead of the CRSC people. Non-taxed seperation pay can be done based of occuring in a combat zone, which is a loser standard and may be reachable in a easier way. Just needs a doc saying the symptoms were 8 months late in being looked at, something like based off the severity and reported symptoms, the asthma likely started 12 months before the EKG while deployed to Afghanistan. Don't even need to talk about cause, just the date of origin.