Blast Injuries

Warning: This page gets rather graphic. Turn back now if you have a weak stomach or an overactive imagination.
Also, some general advice: don't blow stuff up, and don't make bombs. It's dangerous, probably illegal, and you're likely to hurt yourself and others.

Basic Information

Blast Injuries are wounds and damage caused by explosions, either accidental or via a weaponized explosive. They are particularly nasty injuries, and the danger is often underestimated and oversimplified in the rules for bombs in roleplaying games.

Blast Injuries come in four general categories, based on the nature of the explosive and the environment in which it is detonated.

Primary Blast Injuries

Trauma caused by the Blast Wave of a high explosive. This suddenly moving wall of pressure can kill instantly and outright, especially those close to the explosion. Even if you don't die, it's possible the blast could destroy your eyes or ears instantly, causing a permanent disability (even quite minor explosions can rupture the tympanic membrane of the ear - "burst an ear drum" - causing at least a temporary loss of hearing, traditional bleeding from the ears and likely permanent impairment. Likewise, bruising and burst blood vessels in the eye can cause pain and temporary impaired vision even if the victim eventually recovers).

More insidiously, sometimes Primary blast injuries can cause internal injuries that take hours or even days to present as life-threatening. You may think you squeaked by with hardly a scrape, and then drop dead later with little warning.

• Blast Belly is when one of your internal organs (usually a hollow one like the colon or lungs, but possibly any organ even the heart) collapses, is punctured, or even is blown out by the force. Initial symptoms may be nausea, upset stomach, fatigue, or blood leaking from orifices that don't usually bleed.
• Blast Brain is when the force concusses your brain or nervous system. Initial symptoms may be headache, confusion, fatigue or just insomnia.

In some cases, internal blast injuries can leave the recipient almost unmarked - especially when they are killed outright and don't have time for bruising to develop - which can be extremely eerie for those who aren't used to such things. Regardless, these injuries are likely to be almost impossible to treat without access to competent surgical intervention - and even if such things are available, a casualty might well walk away from a blast, thinking themselves lucky to have escaped unharmed with only a headache and a bit of nausea, easily explained by traumatic shock. At which point they go home to sleep it off … and potentially fail to wake.

Thankfully, Primary Blast Injuries are usually¹ only caused by High Explosives and Primary Explosives (see our explosive page). They are not generally caused by Low Order Explosives, such as black powder or gasoline-fuelled explosions.

That said, every July 4 lots of Americans lose fingers when a low-order firework detonates in their hand. Just because an explosion is small or low-grade isn't a guarantee that it won't get ugly.

There are also flash burns inflicted by the explosion - these are not technically blast injuries but should be remembered when thinking about them: these are generated by all sorts of explosives, high and low.

Secondary Blast Injuries

Secondary wounds are caused by shrapnel² propelled by the explosion, either deliberately part of a bomb, or just debris from the environment hurled about by the explosion.

Sometimes shrapnel or debris can travel much faster than bullets, so even a tiny wound might be deep (or through-and-through) and end up being much more dangerous than it seems at first glance, although in general the penetration capabilities of such things are lower than those of bullets and so any armour will tend to be better at keeping them out.

Both Primary and Secondary Blast Injuries are subject to the principle of the Inverse-Square Law. In short, the closer you are to the explosion, the more shockwave force it will deliver and/or the higher density of shrapnel that will be headed your way.

Tertiary Blast Injuries

If a victim is particularly close to the explosion, they may be knocked back or lifted off the ground. Impact injuries when they strike solid ground or nearby structures can be significant.

It gets especially bad if you're inside an enclosed space when the bomb detonates, as you may bounce from one wall to the next like a rubber ball, or the shockwave may ricochet back and hit you a second (or subsequent) time, thus inflicting magnified primary effects.

Quaternary Blast Injuries

Some bombs (or environments) may introduce additional complications and injuries beyond the initial blast effects.

• A dirty bomb poisons or irradiates everyone near the blast, and its contamination effects may be carried on the wind for weeks.
• An incendiary device will cause burns and fires, and may cause smoke inhalation or even Lung Disease even in those lucky enough to avoid being burned.
• Environmental toxins may be unleashed even by a clean bomb, if it lands next to a hazardous chemical.
• Explosions in Space may lead to Space Exposure.

Sources

Bibliography

1. I learned nearly all the above via the page on blast injuries on the website of the National Center for Biotechnology Information.

2. My ex-wife was a medical biller and coder for an orthopedic surgery group, and the first week of July was always especially depressing in her line of work.

Game and Story Use

• Most games probably don't need the level of detail provided above, but if you're playing a game set in a war zone, or where the PCs are bomb squad officers, having the extra detail may provide greater verisimilitude.
  • It's pretty common for games to have explosives do maximum damage out to a set distance, and then drop off immediately to zero damage once your cross that magic line. Simply put, this is unrealistic. The Inverse-Square Law page has rules of thumb and template ideas for more plausibly realistic blast radii with scaling damage by range.
• Games with detailed critical hit charts may find it useful to have 3 or 4 different tables for use with explosive events.
• Games with damage reduction systems where the type of damage matters (such as if a monster or character is immune to blunt trauma, but vulnerable to piercing damage) may find it useful to have the extra detail available.
  • A powerful explosion may do one high-damage blast that's either bludgeoning or sonic damage, and additional blunt trauma if the victim is close enough to be thrown or bounced around and/or is indoors. Then every victim suffers a random number of shrapnel wounds each doing a random amount of piercing damage.
• Different grenade or bomb types may specifically cause either Primary or Secondary wounds exclusively, or at different ranges. If you're playing a game with both a very detailed damage/health system and lots of nuanced item descriptions, a more detailed approach to blast injuries may be a good match for your campaign.
  • The distinction between offensive and defensive hand grenades might be a good example - the offensive type being a blast only device that can be used by advancing troops without too much concern about getting hit by fragments of their own weapons, whilst a defensive grenade, designed to be used from a fortified position (or at least solid cover) is designed to generate a substantial debris cloud as well as a blast. The transition from one to the other may be as simple as a removable metal sleeve, pre-scored and designed to disintegrate into small pieces when exploded.
• The delayed onset of blast belly or blast brain could be used for dramatic effect in your story or RPG. A character at the edge of the blast radius may initially seem to be in the clear, and then take a turn for the worse in a later scene.
  • One way to model this in a game may be to use hit-point damage for the secondary and tertiary wounds, but a constitution save (or its equivalent in your game system) for primary impact. If the first constitution check is failed or passed by a narrow margin, it may trigger an additional check several scenes later.
    • Save or die might even be in order, depending on the size of the bomb and the genre of the game.
• In a espionage or mystery genre or police procedural story, the nature of an explosion might become a valuable clue about the criminal or their secret lair. Was it a High Order blast wave attack, or a Low Order shrapnel-laden improvised explosive device?
  • For more ideas on what can be learned in the aftermath of an explosion, see the explosive page (especially the parts about taggants) and the grenade page (especially the parts about offensive and defensive grenades).

Footnotes

1. Usually - there's a similar phenomenon known as "wind of ball" where a casualty can be injured by the shockwave accompanying a large, fast moving object. The name derives from the powder-and-shot era when it was noticed that it was possible for someone to die from a near miss from a cannonball, as well as from being hit.

2. Using the modern meaning of fragmentation debris, not the old one that was a type of multi-shot round.