Radiation is a mechanic in Mechanism. It affects the player with a lingering damaging effect until the player either dies or survives long enough for the radiation level to decay to safe levels. Radiation amounts are viewable by a Dosimeter.

A baseline environmental radiation level of 100nSv/h is be constantly present, and is not harmful to the player.

A radiation level of 10 μsv will cause a green tint to be applied to the player's screen, a damaging effect occurs at approximately 50 μsv. As radiation level rises, the player takes more damage more frequently. At 100 sv, the player will always take damage every half a second. The player will not take damage more frequently beyond 100 sv, but will still take more damage.

The screen effect changes from a green to a blue tint as radiation exposure increases.

Range and Falloff

By default, all radiation sources have a range of 80 blocks (5 chunks) in all directions, but this can be configurated. Being further away from a source of radiation drastically reduces exposure: exposure is directly proportional to the inverse square of the distance. This means that if you are two blocks away from the source, you'll only take 1/4 of the exposure. Being a chunk away reduces the exposure down to 1/256. Being closer than one block to the source does not increase the player's exposure.

Radiation exposed is not reduced if there are blocks between the player and the source. Exposure only depends on the distance to a source.

If there are multiple sources in range, sum up their influences for the total exposure.


All radiation sources in the environment and radiation dosages in entities are naturally multiplied by 0.9995 approximately every second until they fall to ambient levels. There is no way to artificially hasten this process, except editing the related config values.

The Dosimeter and the Geiger Counter also display the estimated time till total decay.

/mek radiation removeAll can be run to clear all environmental radiation sources immediately.

/mek radiation cure <entity> can be run to cure an entity of all its radiation dosage. Alternatively, dying and respawning also clears all dosage of a player.

Adverse Effects

The only gameplay disadvantages irradiation causes are constant damage and hunger loss, which increases the more irradiated the entity is. Radiation damage bypasses all armor (including the MekaSuit), but is reduced by the Protection enchantment. Radiation damage does not bypass a Totem of Undying, but its trigger does not clear radiation, making it rather ineffective.

Detailed Effects

Each tick, a chance is rolled with the formula 0.1 + randomPercentage * 0.9, where randomPercentage is any number between 0 and 1. Then, a scaled radiation is calculated by the formula (log(trueRadiation)+5)/7, capped between 0 and 1. If the scaled radiation is bigger than the chance, the player takes damage. The exact damage taken is in the form of max(1, ln(1+trueRadiation)). The same number of hunger is also lost.


By wearing the Hazmat suit or the MekaSuit with Radiation Shielding Unit installed, the player can reduce how much environmental radiation affects them, up to 100% environmental exposure immunity. However, existing radiation dosage will not be reduced, and if already irradiated, radiation resistance will not reduce the damage taken.

Radiation is not magic damage, and therefore the Inhalation Purification Unit will not block radiation damage.

Note that milk will not reduce the existing radiation dosage, as it is not a status effect. The only way to reduce existing radiation dosage is by its natural decay, the command mentioned above, or death.

The Resistance status effect or Protection enchantment on armor can protect against radiation damage.

Radiation Sources

  • A Fission Reactor meltdown
  • A reactor waste vent is not properly setup
  • Breaking any machine with waste or radioactive gas such as Polonium still in it
  • Breaking Radioactive Waste Barrels. For reference, a full barrel of nuclear waste (spent or not) will add 5.12 kSv/h of radiation into the world.

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