Explosives and Explosions

There are, generally speaking, three types of explosives commonly available: dynamite, nitroglycerin, and gunpowder or Black Powder.

Dynamite comes in cylindrical sticks, 8 inches in length, 1 1/4 inches in diameter and weighing 1/2 pound each or a double stick that is 16″ in length and the same diameter, they weigh 1 pound each. Dynamite is fairly stable – if thrown, it does not explode upon hitting the ground or an object. If put into a fire, it burns but does not explode. Immersion in water for long periods will ruin the dynamite. Storage for long periods in warm conditions will cause the dynamite to become unstable (It ‘sweats’ nitroglycerin.) Dynamite explodes due to the shock from a detonator (blasting cap,) or due to the shock of a bullet hitting a stick, or nearby explosion. Dynamite within close proximity to an explosion will detonate.

Nitroglycerin is an oil that is kept in small 1 ounce vials. Nitroglycerin is extremely unstable and dangerous to use or carry. Any shock can set it off. For example: Dropping to floor or rapping it with a metal object. Nitroglycerin within medium proximity to an explosion will detonate. High temperatures also make it unstable and flame ignites it. At temperatures above 85 degrees F, nitroglycerin has a 1% chance of exploding each day. At temperatures below 55 degrees F, it is sluggish and difficult to detonate. A successful demolition check is required to detonate nitroglycerin below 55 F (DC of 15).

Gunpowder or black powder, is a “low” explosive rather than a high explosive. Loose gunpowder flares but does not explode; gunpowder must be confined to explode. Gunpowder can be set off by flame or electrical shock, but not by simply being dropped. At this point in history, gunpowder is normally available in 5-pound kegs or cans except for military applications which generally use 50lb kegs.

Explosives are generally detonated with a blasting cap connected to either a lighted fuse or electrical wires.

Blasting caps come in a variety of types, including electric caps, and fuse caps. They are used in commercial mining, excavation, and demolition Electric types are set off by a short burst of current sent by a blasting machine, in this time period a Plunger Detonators are wooden boxes with a T-shaped handle on the top, two brass or iron terminals on a side, and a gear-driven dynamo inside. These devices provide an electrical charge that can be used to detonate electrical blasting caps and the attached explosive device at a precise instant. After the charge is laid, a pair of long electrical wires is run between the charge and the plunge detonator (or a battery) The T-shaped handle is pushed down rapidly (it takes some effort) and sends an electrical charge down the wire to set off the explosives. If the wire is cut prior to this action, then no explosion will occur. When purchased, the plunger detonator comes with 50′ of paired wire, but additional cable may be purchased. The plunge detonator is limited to about 500 yards, as the electrical resistance of the wire becomes too great at longer distances. Batteries are mostly wet-cell devices in this era. Heavy and cumbersome to transport in functional status. The liquid is an acid, which will burn flesh if spilled on it. Batteries used for this purpose are about a cubic foot in size.

Traditional fuse caps have a fuse which is ignited by a flame source, such as a match or a lighter. Fuses are lengths of flammable cord that is connected to a blasting cap. When the cord burns down to the cap, the cap ignites and sets off the explosive device. The length of the fuse can be varied to produce a delay in the time of the explosion. Use of fuses is still fairly common. Because such fuses burn unevenly and at differing rates (and are tricky to light reliably.) Precision timing of an explosion is difficult. As a general rule, a one-yard length of fuse burns in 1 minute. A deviation of plus or minus 10% is considered average. A careful demolitionist will plan for this variance.

Blasting caps (detonator caps) use black powder as the charge, much like a large firecracker, in a cylinder around 1 1/2″ in length and 1/4″ in diameter. Electrical caps have two wires coming out that are connected to a plunge detonator or a battery and switch. In this era, electrical caps are instantaneous. (Electrical delay caps are not yet available.) Fuse caps have a burnable fuse that appears to be a stiff, slick surface cord. Blasting caps can be bought in boxes and are generally stored separate from explosives. Inserting a blasting cap into the explosive is a full round action. All blasting caps contain fulminate of mercury and is sensitive to shock so carrying dynamite with blasting caps attached is dangerous. A shock such as fall on a hard surface could set off the blasting cap and indirectly the dynamite. A blasting cap that is in an individual’s hand or pocket that accidentally detonates, does 1d6+1 damage, possibly blowing off one or more fingers. Save vs Paralyzation. Failure causes the loss of 1 to 3 fingers if held. If in a pocket or tucked in belt and against the body, damage is doubled.

Unlike firearms, explosives have a blast radius that can potentially injure or kill several people, in addition to damaging structures. To reflect this variable area-of-effect, four radial proximity zones (called blast zones) of explosive damage are defined: point blank, close, medium, and far.

# Charges Point Blank Close Medium Far
1-7 1′ 3′ 10′ 15′
8-16 2′ 5′ 15′ 30′
17+ 3′ 10′ 30′ 45′

Dynamite Damage
One 8″ stick of dynamite causes 4d6 hp within point blank, 3d6 hp within close, 2d6 hp within medium, and 1d6 hp within far zones. For each additional 8″ stick of dynamite in a bundle, add 3 hp per d6 of damage to the result.
One 16″ stick of dynamite causes 8d6 hp within point blank, 6d6 hp within close, 4d6 hp within medium, and 2d6 hp within far zones. For each additional 16″ stick of dynamite in a bundle, add 5 hp per d6 of damage to the result.
If the target is a person (sentient being) who is able to move (not helpless), then they get a Reflex saving throw for half damage. This damage is shock (pressure wave and thrown debris), not fire, so magical protections against fire do not protect against dynamite blast damage. Sonic protections do protect against damage from explosions.

If the explosion occurs inside of a room or cave where the volume of the room is less than the far zone of the explosion, then the damage is intensified. Treat any rolled 1’s as 2’s for such cases.

Each vial of nitroglycerin or each 5-pound keg of gunpowder is treated as equivalent explosive damage (and blast zones) as an 8 stick of dynamite.

Gun Powder or Black Powder, is a slow burning explosive and when detonated does fire damage as well as blast or concussive damage. Black powder does 1hp of Flame Damage per OUNCE in a 5′ radius. 1hp of Flame Damage per two ounces in the 5′ to 10′ radius. And 1hp of Flame Damage per 4 ounces in the 10′ to 20′ radius.

Black Powder Example: A 5lb keg of Black Powder is detonated. It causes 4d6 hp within point blank, 3d6 hp within close, 2d6 hp within medium, and 1d6 hp within far zones. Additionally, anyone in point blank or close range (out to 5′) will take 80hp of Flame Damage unless a Save vs Breath Weapon is made, which halves the Fire Damage. Anyone between 5′ and 10′ will take 40hp of Flame Damage unless a Save vs Breath Weapon is made, which halves the Fire Damage. And anyone from 10′ to 20′ from the blast will be hit with a wave of fire and take 20hp of Flame Damage unless a Save vs Breath Weapon is made, which halves the Fire Damage.

Nitroglycerin, much like Dynamite, is a Fast Explosive and produces minimal flame damage. One 1 ounce vial of Nitroglycerine causes 4d6 hp within point blank, 3d6 hp within close, 2d6 hp within medium, and 1d6 hp within far zones. For each additional ounce of Nitro, add 3 hp per d6 of damage to the result.

One of the side effects of an explosion is damage to the hearing of individuals close to the blast. An individual will suffer a temporary hearing loss of 3d6 minutes if inside the Medium or Far blast zones and failed their Reflex saving throw (as above) they will also be stunned for one minute. Individuals inside of the point blank or close blast zone who failed their saving throw will suffer a 50% PERMANENT reduction in hearing and will be knocked down and be stunned for ten minutes.

Dynamite Example One: 5 sticks of 8″ dynamite would cause 3d6 hp plus (4 sticks x 3 (# of dice) x 3 hp/stick/dice = 36 hp of damage), or 3d6 + 36 hp at close proximity to a person.

Dynamite Example Two: 12 8″ sticks of dynamite would cause 2d6 hp plus (11 sticks x 2 (# of dice) x 3 hp/stick/dice = 66), or 2d6 plus 66 hp of damage in the medium blast zone to a person.

Dynamite Example Three: If a person was in the far blast zone to those same 12 sticks of 8″ dynamite, the damage would be 1d6 + 33 hp.


Throwing Explosives

Either dynamite or nitroglycerin may be thrown as a grenade at a target. Gunpowder, generally found in kegs, is too bulky to be thrown. Throwing dynamite or nitroglycerin is treated as a ranged touch attack with the thrown weapon misses rules.

The range increments for throwing bundles of dynamite are 12′ for 1-7 sticks per bundle, 8′ for 8-12 sticks per bundle, and 4′ for bundles of dynamite greater than 12 sticks (but less than 25 sticks). Bundles larger than 25 sticks cannot be thrown.

Even if the ranged touch attack is successful, the dynamite may not explode upon contact. Dynamite requires preparation of a fuse cap and a lit fuse prior to being thrown as a grenade (unless another character is attempting to shoot the stick(s) with her firearm). Judging the proper length of fuse and timing of the throw and predictably lighting the fuse is part of the demolition skill check. A successful check (DC of 18) means the dynamite will explode where it “lands.”

They may take 10 if the bundle is prepped while the demolitionist is not in combat or threatened. An unsuccessful demolition skill check means there is a time delay before the dynamite explodes. The DM should secretly roll initiative (+0) for the dynamite bundle (thereby inserting its explosion into the initiative order) and a 1d10-1 (to determine any delay prior to exploding). For example, the dynamite will explode on its initiative if the delay round result is zero, but if the delay result was 6, it will explode on its initiative after 5 secondss pass. In the meantime the bundle may be picked up and thrown again (maybe back at the attacker, remembering that picking up an item on the ground is a move action).

A demolition skill check (DC 10) may successfully defuse the bundle. Failure causes detonation. A roll of a “1” on the die for any demolition skill check means the dynamite bundle explodes in the thrower’s hand.

(Unless magical aid is forthcoming, such accidents will mean the loss of a hand as surgical techniques are not sufficient to restore the hand.)

In all cases, characters get a Reflex saving throw unless they are helpless (unconscious, asleep, bound up or magically Held). Success yields half damage.

Lighting the dynamite fuse counts as a move- equivalent action. A character can light a fuse and throw the dynamite bundle, but not move more than 5 feet in the same round. Alternatively, the character can light a fuse and make a normal move.

Ranged Touch Attack against target for Dynamite
Attack Roll  
Successful Target is within point blank blast zone
Unsuccessful Use thrown weapon miss rules to determine proximity (1 square per range increment)

Throwing vial(s) of nitroglycerin uses the same ranged touch attack procedure except that nitroglycerin will explode upon “landing,” assuming that it has not already exploded.

The character throwing the nitroglycerin must make a demolition skill check (with use of the dexterity modifier instead of the intelligence modifier) to see if she can throw the nitroglycerin without it exploding in her hand. The DC for success is 20 plus 5 for each additional vial contained in a bundle. (The vials have a high risk of banging into each other while being thrown.) The character cannot take 10 or 20 in this case as it is impossible to throw it slowly and there is an immediate consequence. Failure results in the explosion in the thrower’s hand. (The hand can be assumed to be two feet away from the head or torso, placing the damage in the close blast zone.) If thrown safely, the usual ranged touch attack will determine if the explosion goes off within the point blank blast zone on the intended target or if missed thrown weapon rules are to be used to determine the point of impact (as these vials won’t roll).

When a character throws either dynamite or nitroglycerin, there is a small chance that they might drop the explosive at their feet. If the attack roll was a natural one on the dice, the character must make a dexterity check against DC 10 not to drop the explosive at their feet. Nitroglycerin would immediately explode (close proximity) while the burning fuse on the dynamite would allow an improved chance of escaping the blast. In the latter case, a successful Reflex save results in no damage and an unsuccessful Reflex save yields half damage from close proximity. If the character failed their check to time the explosion (see previous page), the DM should check the explosion’s initiative. He or she might have time to pick the dynamite up and try again to throw it!

Blowing Things Up!

Explosives may be set using the demolition skill to cause structural damage. If the skill check makes the difficulty class (DC) of the task, then the building is demolished, the wall or door is breached, or the tunnel is caved-in. A minimum charge to demolish with a set charge a building or to breach a wall or door of 1-inch thickness is cited below. Vary the charge proportionally to the thickness of the wall or door.

Minimum Set Charge
Target Material Minimum Charge Wall or Door DC (wall/door) Minimum Charge (per 10′ x 20′ room) DC (building)
Wood 1 10 1 15
Earth (unlikely for less than 1 foot walls) 0.25 12 2 20
Brick/Mortar Stone 1 14 3 20
Soft Stone/Concrete 1.5 15 4 25
Hard Stone 2 20 5 30
Iron or Steel 3 25 6 30

For each additional stick of dynamite (or equivalent) added to the charge above the minimum charge, add a +1 modified to the skill check. The character setting the charge may take 10 per the PHB.

Characters with the Engineering skill may also add a bonus of +4 to their demolition skill check for structures.

The DC of collapsing a tunnel or cave is 15 if in earth and 25 if in stone. Characters who also have the mining skill get a bonus of +6 to this skill check. The DM should assign DC to other structures as needed.

The normal successful demolition check also means that the delay for a lit fuse was set correctly. If the demolition skill check exceeds the DC by 10 or more, the demolition was done completely safely (meaning if characters were in another part of the tunnel, it did not collapse on them or an area meant to be protected, was so protected).

Set charges may also be used as part of a trap or as part of an ambush. (Setting mechanical traps may require additional skills.) If the demolition skill check is successful, for determining damage to people (or animals) within the explosion, use the same blast zones as per above. The DC for a trap or ambush using set charges is in the range of 20 to 30, depending upon the complexity of the trap or ambush.