Calima - Sahara Dust Days

Calima is a weather event where strong southeasterly winds carry fine sand and dust from the Sahara across the Atlantic to the Canary Islands. The sky turns orange or milky white, visibility drops, and air quality deteriorates - sometimes severely. During a strong Calima, dust concentrations (PM10) can reach 500–900 µg/m³, far above the 45 µg/m³ the WHO gives as the guideline for daily PM10 exposure.

Checking the current dust load and forecast

Windy, dust mass over Gran Canaria. Two things about the time bar at the bottom:

• The map usually opens at 01:00 of the current day - select the current time first, the small orange mark in the bar.

• The same bar gives the forecast for every single hour of the next three days.

What to do during Calima

• Above 200 µg/m³ - consider keeping windows and outside doors closed and spending as little time outdoors as possible. A good day to train inside.

• 50 to 200 µg/m³ - consider avoiding intense outdoor cardio. Walking, easy sessions and normal daily life are fine.

• Below 50 µg/m³ - normal again for most people. The WHO guideline for daily PM10 exposure is 45 µg/m³.

Windy shows dust only. On a Calima day that is nearly all of what is in the air, so the number works as a rough PM10 reading. Most Calima events pass within one to two days.

We are not doctors and this is not medical advice. If you have asthma or another lung condition, ask yours - your thresholds may be lower.

Air Purifiers - One at Each Location

Each of our three locations - U32 Headquarter, P21 Outpost and J48 Penthouse - has its own air purifier.

During strong Calima, keep windows and outside doors closed as much as possible. During longer episodes, however, occupied rooms still need occasional ventilation to prevent CO₂ from building up. When you need to ventilate, open the windows fully for a few minutes - ideally when the outdoor dust concentration is relatively low - then close everything again and use the air purifier to filter the particles that entered with the outside air.

In practice: after ventilating, put the air purifier at the threshold of your open room door, switch it on and let it run there for about 10 to 20 minutes. That way, your room and the shared area next to it are filtered together.

One exception is the Acro Atrium: its doors open straight to the outside, so run the purifier with your door closed. Set a timer and bring the device back to the dining area after 20 minutes at the latest, so the next person finds it where it belongs.