Elemental proliferation
Elemental proliferation is a modifier that makes hits apply status ailment debuffs as auras to targets; these debuff auras have the same effects and durations as the original debuffs. Nearby enemies affected by these auras do not gain the auras, because only a target that has received a status ailment – as a result of being hit – can gain them. These auras are considered as status ailments, which means there can be more than one proliferation effect on the same target at the same time, but only the strongest one will present itself. The exception to this is if status ailments are allowed to stack, as is the case with 
EmberwakeEmberwake
Ruby RingRequires Level 16+(20-30)% to Fire Resistance(30-40)% increased Fire Damage
(5-10)% increased Cast Speed
10% chance to Ignite
40% less Burning Damage
You can inflict an additional Ignite on an EnemyLeave the world in flames behind you.
.
Modifiers to area of effect radius and damage will apply to status ailment auras. But if a skill cannot be supported by AoE gems (such as 
Increased Area of Effect SupportIncreased Area of Effect SupportSupport, AoE
Icon: E
Level: (1-20)
Cost & Reservation Multiplier: 130%Requires Level 38Supports any skill with an area of effect.Supported Skills have (30-49)% increased Area of Effect
Additional Effects From 1-20% Quality:
Supported Skills deal (0.5-10)% increased Area DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.
and 
Concentrated Effect SupportConcentrated Effect SupportSupport, AoE
Icon: o
Level: (1-20)
Cost & Reservation Multiplier: 140%Requires Level 18Supports any skill with an area of effect, regardless of whether that skill deals damage.Supported Skills deal (25-39)% more Area Damage
Supported Skills have 30% less Area of Effect
Additional Effects From 1-20% Quality:
Supported Skills deal (0.5-10)% increased Area DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.
), proliferation effect will not benefit from them either.
Since status ailments (ignite, chill and shock) stay on corpses after death, debuff auras also stay and spread their effects to enemies around these corpses for the ailment's duration, or until the corpses are destroyed (e.g. shattered due to being frozen, detonated or raised).
Ground effects such as burning or chilling ground do not count as status ailments and therefore will not be proliferated.
Sources of elemental proliferation
Elemental Proliferation SupportElemental Proliferation SupportCold, Fire, Lightning, Support, AoE
Icon: S
Level: (1-20)
Cost & Reservation Multiplier: 110%Supports any skill that hits enemies, or could otherwise apply elemental ailments.(0-19)% increased Duration of Elemental Ailments on Enemies
Elemental Ailments inflicted by Supported Skills spread to other enemies within (1.2-1.5) metres
Supported Skills have 20% chance to Freeze, Shock and Ignite
Additional Effects From 1-20% Quality:
(0.5-10)% increased Duration of Elemental Ailments on EnemiesThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.
Doryani's CatalystDoryani's Catalyst
Vaal SceptreSceptre
Physical Damage: (102-122) to (170-230)
Critical Strike Chance: 6.00%
Attacks per Second: (1.55-1.61)
Weapon Range: 1.1 metresRequires Level 75, 113 Str, 113 Int32% increased Elemental DamageSocketed Gems are Supported by Level 20 Elemental Proliferation
Adds (65-85) to (100-160) Physical Damage
(11-15)% increased Attack Speed
(6-10)% increased Cast Speed
(30-40)% increased Global Critical Strike Chance
0.2% of Elemental Damage Leeched as Life
(80-100)% increased Elemental DamageThe result of the catalytic reaction would be either immortality for all,
or death for all. It was a risk Doryani was willing to take.
Thousand RibbonsThousand Ribbons
Simple RobeEvasion: (30-60)
Energy Shield: (44-80)
Movement Speed: -3%Requires 17 IntSocketed Gems are Supported by Level 5 Elemental Proliferation
Adds (2-4) to (5-9) Fire Damage to Spells and Attacks
Adds (2-4) to (5-9) Cold Damage to Spells and Attacks
Adds 1 to (4-12) Lightning Damage to Spells and Attacks
+(30-60) to Evasion Rating
+(30-60) to maximum Energy Shield
+(25-50) to maximum Life
+(25-50) to maximum Mana
+(15-30)% to Fire Resistance
+(15-30)% to Cold Resistance
+(15-30)% to Lightning ResistanceThe night of a thousand ribbons
To remember the day of a thousand flames
When Sarn burned
And was born again
Ignite Proliferation SupportIgnite Proliferation SupportFire, Support, AoE
Icon: I
Level: (1-20)
Cost & Reservation Multiplier: 130%Requires Level 38Supports any skill that hits enemies.Ignites caused by Supported Skills spread to other Enemies within (1.4-2) metres
Supported Skills deal (15-24)% more Damage with Ignite
Additional Effects From 1-20% Quality:
Supported Skills deal (0.5-10)% increased Fire DamageThis is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.
(ignite only)- Elementalist's passive Beacon of Ruin
Xoph's NurtureXoph's Nurture
Citadel BowBow
Physical Damage: (95.4-106.2) to (381.6-424.8)
Critical Strike Chance: 6.00%
Attacks per Second: 1.25Requires Level 64, 185 DexSocketed Gems are Supported by Level 20 Ignite Proliferation
(165-195)% increased Physical Damage
50% of Physical Damage Converted to Fire Damage
10% chance to Ignite
Recover (40-60) Life when you Ignite an EnemyUpon the grey winds his love spreads.
(ignite only)