The biggest blue fire area in the world is still closed. Descending into the crater of the active volcano Ijen is forbidden since March 6th, 2017. As the volcano releases toxic gasses mainly during the night, visitors officially aren't allowed to see the blue fire. One can still climb the mountain.

Sign: forbidden to descend to Ijen crater lake - closed since 05 March 2017

Volcanology closed the crater for visitors at the 6th of March after sulphur miners got caught by the gasses and were evacuated. Although the crater lake is closed during the night, the status of the volcano isn't increased. Visitors can climb the volcano starting at 03.00, normally at 02.00, but aren't allowed to descend into the crater. Sulphur miners aren't allowed to mine during the night either.

Toxic reactions

The temperature of the water in the lake increased, according to Eka Muharram, the head of Emergency Disaster (BPBD) in Banyuwangi. Small eruptions inside the crater release toxic gases sulphur dioxide (SO2), carbon dioxide (CO2), and sulfuric acid (H2S). This release of toxic gasses is related to the water level and the water temperature at several depths of the lake and small explosions that release these toxic gasses.

Violations of the rules

Although miners aren't allowed to mine during the night, some still do, despite the regulation. Some of them also take guests to the lake. Please keep in mind that when you still want to visit the lake, nobody can or will take responsibility in case something happens as you violate the rules.
If you are still keen on seeing the blue fire, you can start walking at 03.00 and try to see the blue fire from the edge of the crater. This of course is less spectacular then standing "in it", but better than nothing at all. If you aren't descending into the crater, you won't need a guide.

 

Sources:

* Ardian Fanani, 6 March 2017. Kawah Ijen keluarkan gas beracun, wisatawan dilarang lihat blue fire. https://news.detik.com/berita-jawa-timur/d-3439845/kawah-ijen-keluarkan-gas-beracun-wisatawan-dilarang-lihat-blue-fire
* Ira Rachmawati, 9 May 2017. Pendaiki dilarang mendekati "Api Biru" di kawah Ijen. http://nationalgeographic.co.id/berita/2014/05/pendaki-dilarang-mendekati-api-biru-di-kawah-ijen
* Drivers and guides of Ijen Plateau