Dives with compressed air to more than 40 m depth - the Swiss perspective

In our diving school, we have recently discussed the topic of compressed air dives to depths of over 40 meters on several occasions. A topic that certainly interests many enthusiastic divers. This blog post aims to provide an assessment from a Swiss perspective.

Walensee. Image template: Karin Aggeler

Nitrogen narcosis

Limiting dives with compressed air to a maximum of 40 m is generally generally accepted today and is considered standard worldwide. The main reason for this is to avoid nitrogen narcosis (depth intoxication). This also applies to Switzerland. Article 52 of the Compressed Air Ordinance of 2015 stipulates a maximum diving depth of 40 m for underwater work under compressed air and allows a maximum nitrogen partial pressure of 4 bar.

The gas density

In my opinion, gas density is a completely underestimated problem. With increasing diving depth, the density of the breathing gas increases due to the ambient pressure. It has long been recognized among diving physicians that the maximum breathing gas density should not exceed 6.2 g/l, as problems of any kind increase exponentially beyond this value. Excessive work of breathing reduces the diver's reserve capacity to cope with physical exertion in the event of an emergency.

Anthony and Mitchell recommend that a gas density of 5.2 g/l should ideally not be exceeded, and set the absolute upper limit at 6.2 g/l. Unfortunately, these limits have so far been widely ignored, most likely for reasons of logistics - strict compliance would only be possible with the use of helium. However, the BSAC (Britsh subaquatic club), for example, has included them in its guidelines. A value of 6.2 g/l is exceeded with compressed air at a temperature of 20 °C from a depth of 43 m at the latest, and at lower temperatures even at shallower depths.

The hazard

The Federal Council may define special hazards and risks that lead to the refusal of all benefits or to reductions in benefits under non-occupational accident insurance. According to Art. 50 para. 2 UVV, risks are acts by which the insured person exposes him/herself to a particularly great danger without taking or being able to take precautions to limit the risk to a reasonable level.

In general, diving with compressed air at depths of more than 40 m is considered a hazardous act, because beyond this depth the risk of nitrogen narcosis increases significantly. Moreover, it can generally be assumed that the deeper one dives, the greater the problems and thus the dangers (see above). This limit of 40 m was confirmed in 2010 following a discussion between various Swiss diving organizations on the one hand and insurance companies (including SUVA/Swiss National Accident Insurance Fund) on the other.

SUVA's practice offers some leeway in that dives with compressed air up to a depth of 50 m can (but do not have to!) be denied the character of a risk if they are carried out by divers with exceptionally good training and exceptionally extensive experience. As a rule, only diving instructors fulfill these requirements.

On this basis, SUVA considers diving deeper than 40 m to be an absolute risk. However, there is also a ruling by the Federal Supreme Court which describes diving deeper than 40 m as a relative risk.

In the case of an absolute risk, insurance cover is provided - except in particularly serious cases - but the cash benefits are reduced by 50%. Risks only apply to non-occupational accidents. In the case of occupational accidents, there is a theoretical possibility of a claim for compensation!

For divers with exceptionally good training and exceptionally extensive experience - and this usually includes diving instructors - a limit of 50 m does apply.

Under no circumstances should this be interpreted as a license to plan 50 m dives with compressed air. At best, this is a somewhat ambiguous area, not least for divers who perform 50 m dives as part of their job, such as police or military divers. There is also the theoretical possibility of recourse in the event of occupational accidents.

Illness - always unfavorable

There is also another, often overlooked problem. The above only applies to accidents. By legal definition, an accident is a sudden, unintentional harmful effect of an unusual external factor on the human body that results in impairment of physical, mental or psychological health or death. If one of these aspects is missing, the event is not classified as an accident but as an illness. In the case of a diving incident, it should therefore first be checked whether it is considered an accident at all.

A decompression incident is considered an illness and the above would not apply in this case. Treatment in a hyperbaric chamber is therefore covered by health insurance. This is only good news at first glance, as many divers do not have daily allowance insurance for illness. This means that if you are unable to work due to a serious decompression illness, you may have to reckon with a significant loss of pay. Also, the cash benefits in the event of permanent disability due to illness are often much lower than in the event of an accident. This would also apply to (partial) disability due to decompression illness.

Conclusion

For the medical reasons mentioned above, diving with compressed air to depths of over 40 m is strongly discouraged, especially considering the potential insurance implications in the event of an incident.

Furthermore, in the event of decompression sickness, there is a risk of significant loss of compensation in the absence of daily allowances insurance and, in the event of permanent disability, lower disability pension entitlements.

Diving organizations should consistently limit compressed air dives to a depth of 40 meters, regardless of the circumstances. This not only protects their members from potential health risks, but also from insurance-related uncertainties.