Scientists have sounded the alarm over a toxic smoke cloud blanketing Thessaloniki’s skies following a major fire that broke out in Orfeas (Oraiokastro) on Saturday, 4 July 2026, and continues to burn across two industrial facilities in the area. The dense smoke has shrouded the city, while ash and soot have accumulated on balconies and courtyards across Oraiokastro.
What’s in the smoke?
Professor Dimosthenis Sarigiannis, Environmental Engineering expert at Aristotle University of Thessaloniki (AUTH), explained both the nature of the hazardous plume and key precautions residents should take until the smoke fully dissipates — and until the last embers in the Oraiokastro factories are extinguished.
“This cloud covering Thessaloniki’s sky consists of fine particulate matter produced by incomplete combustion,” he told Voria.gr. “The situation is further complicated by a mix of forest fire emissions and burning industrial materials — including recyclables, detergents, and oils — which significantly worsens the chemical composition of the smoke.”
The airborne particles include volatile organic compounds, particularly irritating to the throat and eyes. Carcinogenic substances such as benzene, dioxins, and furans have also been identified in the plume.
Health risks and vulnerable groups
While most people may experience only mild irritation — like throat tickling or eye discomfort — especially as the fire subsides and the smoke lifts, Professor Sarigiannis warned that these pollutants can penetrate deep into the lungs and even enter the bloodstream, potentially causing longer-term health effects.
Professor Nikos Tzanakis, Pulmonology expert at the University of Crete and Vice President of the Hellenic Thoracic Society, emphasized the need for caution: “Citizens must not relax their vigilance. Those with chronic obstructive pulmonary disease (COPD), asthma, serious heart conditions, or diabetes should strictly avoid outdoor exercise and manual labor. Pregnant women and children — as more vulnerable groups — require special protection. The clear recommendation is to minimize outdoor exposure altogether.”
Practical protective measures
To reduce risk, Professor Sarigiannis advised keeping windows closed and, if going outside is unavoidable, wearing high-filtration masks — specifically KN95 or FFP2 models. Residents are also urged to avoid travel near the fire-affected zone in Oraiokastro.
Regarding air conditioning, he recommended using the internal air recirculation mode — available in most modern units. For older systems lacking this feature, he suggested cooling rooms with fans placed in front of bowls of ice for natural, low-risk relief.
Many residents expressed cautious optimism after meteorological forecasts indicated possible rain — a development expected to help clear the air.