Mont Blanc allegedly has the highest number of fatalities of all mountains in the world, claiming between 6,000 to 8,000 fatalities to date, that's around 100 climbers per year. However, it's important not to confuse the difficulty of a route with danger, the easier and busier routes to Mont Blanc involve all the dangers inherent of the more technical routes.
To limit risks when climbing Mont Blanc it's important to factor in:
Altitude
Lack of oxygen at altitude can cause acute mountain sickness: headaches, insomnia, breathlessness, loss of appetite, nausea, vomiting…the main symptoms can appear even at 3,500m. Proper acclimatisation can help prevent AMS however once the symptoms appear there is nothing to do but start your descent.
Weather
At high altitude the weather can change very quickly, bringing all kinds of difficult conditions such as fog, cold temperatures, violent winds, snow, frost, storms and lightning. It's important to be able to recognise warning signs and to pay attention to forecasts.
Getting lost
One of the main dangers is getting lost in sudden cloud, particularly close to the summit or between the Aiguille du Midi and the Dôme du Goûter. Never set out without a map, navigation instruments and the knowledge of how to use them. Know precisely where you are during your entire itinerary.
Falling
The danger of falling increases with the steepness of the slope. Good technique and suitable roping methods are essential.
Busy periods
The presence of other groups is reassuring, however the presence of other people offers a false sense of security. During the busiest periods (July and August), having to slow down and even stop for others adds further difficulties to crossings and can increase exposure to hazards and high-altitude risks as well as cold and bad weather for longer periods of time.
Fatigue
Altitude, cold temperatures, height gain and increased effort can result in severe fatigue. It's important that group members look out for one another.
Crevasses
Appropriate roping techniques and crevasse rescue equipment on each climbers harness are essential as well as knowing how to use them.
Serac falls
Seracs can fall at any time, without warning, particularly under the Mont Blanc du Tacul, around the Petit Plateau and the Grand Plateau. Avoid these areas or if not, at least do not linger there.
Avalanches
After a period of bad weather, extra care should be taken on gradients of more than 30°. Remember to take an avalanche transceiver, shovel and probe and know when it's best to wait.
Rock falls
Whether natural or caused by other climbers, these demand the greatest care, particularly whilst within the Goûter couloir. Wearing a helmet is essential for this reason.
Ability
Whilst some may tout Mont Blanc as 'just a long walk', some of those in the know recommend having at least six alpine peaks under your belt before you attempt Mont Blanc. Be aware of what you can and can't do, and also what you should or shouldn't do. Don't just rely on your guide. If something doesn't feel right, don't feel pressured into pushing for the summit. There's a reason Mont Blanc is one of the world's deadliest mountains.
More information on routes, safety and preparation can be found on the Fondation Petzl site here.