lundi 12 mai 2025

Scuba Diving Physic

PHYSIC

PRESSURE IN SALT WATER

AT 20M THE PRESSURE IS 3 BAR

FORMULA:

20M / 10 +1 = 3BAR

SW ATM PRESSURE

PRESSURE IN FRESH WATER

AT 20M THE PRESSURE IS 2.94BAR

FORMULA

20M / 10.3 +1 =2.94 BAR

FW ATM PRESSURE

GAUGE PRESSURE VS TOTAL/AMBIENT PRESSURE

THE GAUGE PRESSURE IS THE AMBIENT PRESSURE WITHOUT THE SURFACE PRESSURE

FORMULA GAUGE PRESSURE

20M / 10 = 2BAR

20M / 10.3 = 1.94BAR

THE TOTAL OR AMBIENT PRESSURE IS THE SAME, WE COUNT THE PRESSURE FROM THE SURFACE

FORMULA

20M / 10 +1 = 3BAR

SW SURFACE PRESSURE

20M / 10.3 +1 = 2.94 BAR

FW SURFACE PRESSURE

TEMPERATURE CHANGES ( CHARLES’ LAW)

IF TEMPERATURE INCREASE, THE PRESSURE INCREASE
IF TEMPERATURE DECREASE, THE PRESSURE DECREASE
THE PRESSURE INCREASE OR DECREASE FROM 0.6 BAR PER DEGRES

FORMULA

FILL TANK TO 200BAR TEMPERATURE OF THE TANK IS 40C WHEN FULL

THE NEXT MORNING THE TANK TEMPERATURE IS 30C

CALCULATON:

40C – 30C = 10C

10C X 0.6 = 6 BAR

200BAR – 6 BAR = 194 BAR

AIR COMSUPTION

THE DEEPER YOU GO THE MORE AIR YOU USE
SHE SHALLOWER YOU YO THE LESS AIR YOU USE

FORMULA

PUT ON PAPER LIKE THIS:

CHANGE THE METERS TO BAR (BE CAREFULL IF FRESH OR SALT WATER)
BRING YOUR COMSUPTION TO THE SURFACE ( LESS SO DIVIDE)
BRING YOUR COMSUPTION DOWN (MORE SO TIME)
FINISH
ALWAYS BRING IT TO THE SURFACE 1^ST

VOLUME CHANGES (BOYLE’S LAW)

IF THE PRESSURE INCREASE, THE VOLUME DECREASE
IF THE PRESSURE DECREASE, THE VOLUME INCREASE

FORMULA:

PUT ON PAPER LIKE THIS:

CHANGE THE METERS IN BAR (BE CAREFULL OF FRESH OR SALT WATER)
BRING YOUR VOLUME TO THE SURFACE ( MORE SO TIME)
BRING YOUR VOLUME DOWN ( LESS SO DIVIDE)
FINISH
ALWAYS BRING TO THE SURFACE 1^ST

FRESH WATER:

ANSWER

WEIGHT OF WATER

1LT OF FRESH WATER WEIGHTS 1.0 KG
1LT OF SALT WATER WEIGHTS 1.03 KG

FORMULA

10LT FW X 1 = 1KG

10LT SW X 1.03 = 1.03KG

ARCHIMEDE’S PRINCIPLE

IF YOU PLACE AN OBJECT IN THE WATER, THIS OBJECT WILL DISPLACE WATER.

IF THE WEIGHT OF THE WATER DISPLACED IS LESS THAN THE WEIGHT OF THE OBJECT, THE OBJECT WILL SINK (COIN IN WATER)
IF THE WEIGHT OF THE WATER DISPLACED IS MORE THE THE WEIGHT OF THE OBJECT, THE OBJECT WILL FLOAT
IF THE WEIGHT OF THE WATER DISPLACES IS THE SAME WEIGHT AS THE OBJECT, THE OBJECT WILL BE NEUTRAL

BE CAREFULL IF THE OBJECT IS IN FRESH OR SALT WATER
YOU NEED TO KNOW: THE WEIGHT OF THE OBJECT (KG), THE VOLUME OF WATER DISPLACED (LT) AND IF IN FRESH OR SALT WATER
IF YOU DON’T HAVE THESE NUMBERS, YOU CANNOT CALCULATE!!!

FORMULA:

ALWAYS PUT ON PAPER AND WRITE IF KG OR LITERS
YOU CANNOT DIVIDE KG BY LT

CHANGE THE WATER(LT) IN KG
MINUS YOUR RESULT TO THE WEIGHT OF THE OBJECT
IF YOU FIND – IN FRONT OF THE NUMBER, THE OBJECT SINK(NEGATIVE BUOYANCY)
TO FIND HOW MUCH AIR YOU NEED TO ADD IN LIFTING BAG, CHANGE THE KG IN LITER AGAIN AND YOU GET YOUR ANSWER
BE AWARE OF FRESH OR SALT WATER

ANSWER:

PARTIAL PRESSURE ( DALTON’S LAW)

IN A MIXTURE OF GASES, THE TOTAL PRESSURE OF THE MIXTURE IS EQUAL TO THE SUM OF THE 2 GASES

FORMULA:

IN AIR WE HAVE O2 AND N2 OR SOME OTHER GASES WHO ARE TO SMALL TO BE COUNTED

O2 AROUND 21%

N2 AROUND 79%

AT THE SURFACE , THE PRESSURE IS 1 BAR

THE TOTAL OF O2 AND N2 HASE TO BE EQUAL TO 1

TO FIND THE PARTIAL PRESSURE, DIVIDE THE % BY 100

SURFACE WITH AIR 1 BAR TOTAL PRESSURE

EXEMPLE: 21% 02 / 100 = 0.21 PPO2

+79% N2/ 100 = +0.79 PPN2

------- -------------

TOTAL 100% 1 BAR

10M WITH AIR SW 2 BAR TOTAL PRESSURE

EXEMPLE: 21% 02 / 100 = 0.21 PPO2 X2 = 0.42 PP02

+79% N2/ 100 = +0.79 PPN2 X2 = +1.58 PP02

------- ------------- ------------

TOTAL 100% 1 BAR 2BAR

WHY WE NEED TO KNOW THE PARTIAL PRESSURE
O2 IS TOXIC AT 1.4 PPO2 à CONVULTIONS
N2 IS TOXIC AT 2.23PPN2 (18.3M) à NITROGEN NARCOSIS

HOW TO CALCULATE THE MAX DEPTH WITH PPO2:

MAX DEPTH = 14 EMERGENCY DEPTH 16

---- -10 CONTENGENCY DEPTH --- - 10

FO2 FO2

EXEMPLE: DIVING WITH AIR 21%O2

14 16

--- -10 = 56.6M --- -10 = 66.19M 0.21 0.21

EXEMPLE: DIVING WITH NITROX 32%

14 16

--- -10 = 33.75M --- -10 = 40M 0.32 0.32

HENRY’S LAW

HENRY’S LAW STATE THAT WE ABSORB NITROGEN TO TRY TO EQUILIZE THE AMBIENT PRESSURE WITH OUR INSIDE BODY PRESSURE
THE DEEPER WE GO THE MORE DENSE THE AIR IS SO WE ABSORB NITROGEN FASTER
WE ABSORB NITROGEN UNTIL OUR BODY IS SATURATED WITH N2 (NON DECOMPRESSION LIMIT)
WHEN WE COME UP TO THE SURFACE, OUR N2 PRESSURE INSIDE OUR BODY IS HIGHER THEN THE AMBIENT PRESSURE SO WE RELEASE N2
WE ABSORB N2 MUCH FASTER THEN WE RELEASE IT.

LIGHT

LIGHT IS REFLECTED ON THE SURFACE OF THE WATER
THAN IT IS DIFFUSE AND ABSORB IN THE WATER
BECAUSE OF THAT, WE LOOSE COLORS
1^ST IS RED, THAN ORANGE, THAN YELLOW, THAN GREEN, THAN BLUE
OUR BLOOD AT 3M IS GREEN AND DARK BROWN AT 10M
WE NEED LIGHT OF FLASHES TO SEE THE REAL COLOR UNDERWATER

LIGHT à REFRACTION

UNDERWATER, OBJECTS LOOKS BIGGER BY 33% AND CLOSER BY 25%
THIS IS CAUSE BY WATER AND LIGHT WHO TRAVEL SLOWER IN THE WATER.

LIGHT à TURBIDITY

TURBIDITY CAUSES OBJECT TO LOOK FARTHER AWAY THAN THEY REALLY ARE.

SOUND

SOUND TRAVEL ABOUT 4X FASTER IN THE WATER
IT IS DIFFICULT TO KNOW WHERE THE SOUND COME FROM
OUR BRAIN THINK THAT THE SOUND COME FROM OVERHEAD BECAUSE THE SOUND ARRIVES IN BOTH EARS AT THE SAME TIME

HEAT

WE LOOSE HEAT 25X FASTER IN WATER
THE BIGGEST LOOSE IS BY CONDUCTION( THE WATER TOUCH THE SKIN AND DICIPATE THE HEAT)
USE A WETSUIT TO PROTECT AGAINST IT.
75% OF THIS HEAT GOES AWAY BY THE HEAD, SO IF YOU FEEL COLD PUT A HOOD.

dimanche 11 mai 2025

Scuba Diving Physiology

we have 2 system in our body: cardiovascular system and respiratory system

Cardiovascular system:

heart has 2 functions:

pump rich blood( O2) to the tissues via arteries, and pump poor blood (CO2) from the tissues via veins
pump poor blood (CO2) to the lungs via arteries and pump rich blood (O2) to the heart

the O2 and CO2 is exchange via Capillaries to and from the tissues

if we have too much CO2 it is called Hypercapnia
if we have not enough O2 it is called Hypoxia
if we have too much O2 it is called Hyperoxia or O2 toxicity

the heart beats approx 60 to 80 times per minutes and pump 5lt of blood per minutes

the O2 and CO2 is transported to and form the tissues via the red blood cells

respiratory system

the lungs is where gas exchange occur.

1^st the air enter the trachea then the bronchioles and then the alveoli.

The alveoli are cover by capillaries and it is where the gas exchange

lungs capacity: (around 6.8lt of air)

total lung capacity – from total collapse to full inflation
vital capacity – total amount of air inhaled after maximal expiration
residual volume – the amount of air left in the lungs after maximal expiration
tidal volume – the volume of air who is exchanged during inhalation and exhalation

we breath around 12-20x per minute

we need to breath to decrese the CO2 level in the blood not because we don’t have enough O2

because the air we breath at depth is denser, it is more difficult to breath. To compensate, you need to breath more slowly

the response to stress from our body is to breath shallower.

By doing that, we don’t exchange enough new air from the regulator and by breathing the same air again and again, our body tells our brain that the level of CO2 is to high and we need to breath.

The best way to stop this pattern ( feeling that we don’t have enough air), breath deeply until you feel better. Otherwise panic occurs.

TEMPERATURE

We loose temperature 25X faster in the water than in the air

The most affected is by conduction

The least affected is by radiation

TOO COLD

· Mild Hpyothemia: (body react) not dangerous if handle correctly- don’t need hospital

1. when the body core temperature (inside the body) is too low (less than 37)

2. symptoms : shivering, difficulty to move the extremities

3. best thing to do : stop the dive and dry off, drink hot fluids

1. Advanced hypothermia: (body stop reacting) dangerous- need hospital

1. fail to handle mild hypothermia

2. symptoms : no shivering, feeling hot again, blackout, death

3. best thing to do: stop the dive, dry off, treat for shock while transporting to hospital

TOO HOT

· Heat exhaustion: (body react) not dangerous if handle correctly – don’t need hospital

1. when the core body temperature is to hot

2. symptoms : heavy perspiration (sweat) , cool skin, normal color, nausea

1. best thing to do: shower, drink, jump in water, open the wetsuit, go away from the sun

· Heat stroke : (body stop reacting) dangerous – need hospital

1. fail to handle heat exhaustion

2. symptoms : skin is hot, red, and the sweat stop, blackout , death

3. best thing to do : protect from heat, wet towels, treat for shock while transporting to hospital

SQUEEZE (BAROTROMA)

A squeeze occur when the pressure outside and air space is more than the pressure inside

Don’t attempt to forcefully equalization, you can break the round window in the middle ear

If you don’t equalize you ears, you can break the eardrum who produce vertigo because cold water enter in the middle ear

It can happen in:

1. THE EARS - equalize all the way

2. THE MASK – add air by blowing with the nose

3. THE DRYSUIT – add air on the way down

4. THE LUNGS – never empty your lungs on descent

5. THE SINUSES – equalize all the way

REVERSE BLOCK

A reverse block can happen when the pressure inside an air space is more than the pressure outside and the air cannot escape

It can happen in:

1. THE EARS – never take decongestion pills before diving

2. THE LUNGS – holding the breath on ascent

3. THE SINUSES - never take decongestion pills before diving

If it happen, go down a little a ascent very slowly and

ONLY DIVE IF YOUR SINIUSES ARE HEALTY

SINUSES:

We have 4 pairs of sinuses:

1. frontal sinuses – above the eyes

2. maxillary sinuses – below the eyes

3. ethmoidal sinises – base of the nose

4. spenoidal sinuses – deep inside the skull

EARS : the ears are divided in 3 parts:

1. the outer ear (the part that we see outside until the eardrum

2. the middle ear (the part who is the most affected by pressure)

3. the inner ear (who is in the skull and is not affected by pressure

when we equalize, we push air from the sinuses into the Eustachian tube and add air to the middle ear.

DECOMPRESSION ILLNESS (DCI)

Is divide in 2 groups :

1. Decompression sickness

2. lungs overexpansion

Decompression sickness:

Nitrogen goes out of solution

Causes: - too fast up (max 9m / minute)

- stay too long (ndl limite) non decompression limit

- stay too deep (ndl limite)

predisposing factors:

- dehydratation (water is taken from the body to rehydrate the dry air from the cylinder)

- alcool

- obesity (slow tissues release N2 slower)

- injury

- smoking (CO2 bonds 200x better with red blood cells than O2)

- lack of sleep

- illness ( the body focuses on the part to repair and send O2 and N2 in that place 1^st)

- poor fitting equipment

- certain drug

- decompression dive

symptoms: - joint pain

- tingling

- Numbness

- irritation

- swelling

- extreme fatigue

- weakness

- paralysis (when the bubbles are around the spinal cord)

- black out

- convulsion (when the bubbles are in the brain)

- nausea

- vomiting

- shortness of breath

- shock

- death

1^st aid: - 100% o2 for 30’

- treat for shock

- lay down in recovery position

- transport to hospital

- call DAN (diver alert network)

LUNGS OVEREXPANTION

4 DIFFERENT KINDS:

1. Air embolism

2. mediastinal emphysema

3. subcutaneous emphysema

4. pneumothorax

AIR EMBOLISM: air inside the bloodstream

MEDIASTINAL EMPHYSEMA : air in the middle of the chest

SUBCUTANEOUS EMPHYSEMA : air under the skin

PNEUMOTHORAX : collapse lungs

causes: holding the breath on ascent (most dangerous between 10m and the surface) 1.0m DIFFERENCE CAN CAUSE LUNGS OVEREXPANTION

symptoms : SAME AS THE DCS

- joint pain

- tingling

- Numbness

- irritation

- swelling

- extreme fatigue

- weakness

- paralysis

- black out

- convulsion

- nausea

- vomiting

- shortness of breath

- shock

- death

1^st aid: - 100% o2 for 30’

- treat for shock

- lay down in recovery position

- transport to hospital

- call DAN (diver alert network)

NITROGEN NARCOSIS

Causes : high partial pressure of N2 (nitrogen) the Meyer-Overton theory

It can happen as shallow as 24meters

Symptoms : like to be drunk :

- euphoria

- confusion

- foolish behaviors

- impaired coordination

- false sense of security

- fixation of idea

- visual hallucinations

- deterioration of reasoning

1^st aid : ascent to shallower depth

CONTAMINED AIR

Causes : Improper filling intake of the compressor (Carbon monoxide, oil vapors)

Avoid: smell and taste the air before diving, fill in a trusted diveshop

Symptoms: - headache

- red lips

- red finger nails

1^st aid : - stop diving

- 100% O2

- Hospital if needed

OXYGEN TOXICITY

2 KINDS : CNS (central nervous system or pulmonary)

CNS: due to high partial pressure of O2 more then 1.4 ppO2

Symptoms:

- visual disturbances

- ear ringing

- muscle twitching

- vomiting

- convulsions

1^st aid : stop the dive

PULMONARY O2 TOXICITY : too long exposure to high ppO2

Symptoms :

- burning sensations in the lungs

1^st aid : stop diving until it’s gone

GASES:

O2 : OXYGEN

O2 is about 20.9% of the air that we breath

O2 is transported by the red blood cells, and is absorb via the lungs (alveoli) to the circulatory system by the capillaries

O2 is good for us if the partial pressure don’t pass 1.4ppo2

Minimum ppo2 to stay conscious is 0.10 ppo2

We use 100% of O2 to any diving related problems. Its provide the tissues with more O2 than normal air.

N2 : NITROGEN

N2 is about 78 % of the air that we breath.

N2 is transported by the red blood cells and absorb by the tissues if we dive because of the pressure differential.

Without diving, the N2 is not absorb by our tissue

N2 causes nitrogen narcosis when under high partial pressure

CO : CARBON MONOXIDE

CO is produce by burning materials :

Cigarette à it takes 12 hours to clean the body from 1 cigarette

Gasoline à when petrol driven compressor is used to fill cylinders, a small or big amount can be find inside the cylinder.

The intoxication produce light head, strong headache, excessive hyperventilation , confusion and black out

It can be very dangerous to have even a small amount if it in the cylinder while the air that we breath is denser than at the surface. Always be sure that the filling station and filters are clean and changed as the manufacturer recommends.

CO2: CARBON DIOXYDE

CO2 is produce by the muscles who use the O2 to produce power. The waist product is CO2. High level of CO2produces Hypercapnia (too much of CO2) and tells the brain to breath.

A : ARGON

argon is present I air in a very small quantity.

In diving it is used for dry suit inflation since it have about twice the isolation capacity than air.

He : HELIUM

Helium is present in air in a very small amount

In diving, it is use to counter the effect of nitrogen narcosis is tech diving

Heliox is a mix of helium and O2 with no N2

Trimix is a mix of Helium, O2 and N2

Both of them are use in tech diving

samedi 10 mai 2025

Balanced 1st stage or unbalanced 1st stage difference en plongee

En plongée, balanced first stage (premier étage compensé) et unbalanced first stage (premier étage non compensé) désignent deux types de régulateurs qui diffèrent principalement par la manière dont ils gèrent la pression pour fournir de l'air au plongeur.

Voici les différences principales :

🔧 1. Balanced (Compensé) – Premier étage compensé

✅ Avantages :

Fournit une pression intermédiaire constante quelle que soit la pression dans la bouteille.
Meilleure performance à profondeur et basse pression (quand la bouteille est presque vide).
Idéal pour les plongées profondes, techniques ou en eau froide.

🛠️ Fonctionnement :

Un système de compensation interne ajuste la force du ressort en fonction de la pression ambiante et de la pression de la bouteille.
Le débit d’air reste stable et fluide tout au long de la plongée.

🛠️ 2. Unbalanced (Non compensé) – Premier étage non compensé

❌ Inconvénients :

La pression intermédiaire diminue à mesure que la pression de la bouteille baisse.
Résultat : respiration peut devenir un peu plus difficile en fin de plongée ou en profondeur.
Moins performant en eau froide.

✅ Avantages :

Plus simple mécaniquement.
Moins cher.
Moins d’entretien.

🛠️ Fonctionnement :

La force exercée par la haute pression du bloc agit directement sur le mécanisme.
Pas de système de compensation → le débit d’air peut varier.

🧭 En résumé pour un plongeur :

Critère	Balanced (Compensé)	Unbalanced (Non compensé)
Débit d’air constant	Oui	Non
Performance en profondeur	Excellente	Moyenne
Prix	Plus élevé	Moins cher
Entretien	Plus complexe	Plus simple
Idéal pour	Plongée profonde, technique, eau froide	Plongée loisir peu profonde

vendredi 9 mai 2025

La loi de Boyles et la plongee

La loi de Boyle-Mariotte, souvent appelée simplement loi de Boyle, est une loi fondamentale en physique qui joue un rôle crucial en plongée sous-marine. Voici une explication claire et son lien avec la plongée :

📘 Loi de Boyle (ou Boyle-Mariotte)

Formulée au 17e siècle, elle énonce que :

À température constante, le volume d’un gaz est inversement proportionnel à la pression exercée sur ce gaz.

En formule :

P \times V = \text{constante}

P = pression
V = volume

Cela signifie que si la pression augmente, le volume diminue, et si la pression diminue, le volume augmente, tant que la température ne change pas.

🌊 Application en plongée sous-marine

En plongée, la pression ambiante augmente avec la profondeur :

À la surface : 1 bar (pression atmosphérique)
À 10 m : ~2 bars
À 20 m : ~3 bars
etc.

📌 Exemples concrets :

Volume des poumons / de l’air dans le gilet stabilisateur :
- Si tu descends sans ajuster ton gilet, l'air à l’intérieur se comprime, donc le volume diminue, ce qui augmente la vitesse de descente.
- Inversement, en remontant, l'air se dilate → il faut purger l’air pour éviter une remontée trop rapide.
Masque facial :
- En descendant, le volume d'air à l’intérieur du masque diminue. Il faut souffler légèrement par le nez pour équilibrer la pression et éviter l’effet de « ventouse ».
Accident barotraumatique :
- En cas de remontée rapide en apnée (sans expiration), l’air dans les poumons se dilate : risque de surpression pulmonaire, potentiellement grave.

✅ À retenir :

À mesure que tu descends, l’air se comprime.
À mesure que tu remontes, l’air se dilate.
Toujours compenser et contrôler ta flottabilité.
Ne jamais retenir ta respiration en plongée avec bouteille.

jeudi 8 mai 2025

La loi de Charles et la plongee

La loi de Charles est une des lois fondamentales des gaz, très importante en plongée sous-marine car elle aide à comprendre comment le volume d’un gaz change en fonction de la température.

🔬 Loi de Charles (ou loi de Gay-Lussac)

Formule :
👉 V₁ / T₁ = V₂ / T₂
(si la pression est constante) ou perte de 0.6 bar par degres C

Cela signifie que :

Le volume d’un gaz est proportionnel à sa température absolue (en kelvins) si la pression reste constante.

🌊 Application en plongée sous-marine

Même si la pression change constamment en plongée, la loi de Charles reste utile dans plusieurs situations :

1. Stockage des bouteilles de plongée

Si une bouteille est remplie à haute température (par exemple après un remplissage rapide), la pression augmentera.
En refroidissant, la pression redescend, ce qui peut donner l'impression qu'elle a été mal remplie.
➤ C’est une conséquence de la loi de Charles (et aussi un peu de Boyle-Mariotte).

2. Volume d’air dans les combinaisons étanches ou les gilets stabilisateurs

À température constante, l'air injecté reste stable.
Mais en eau froide, le volume d’air diminue un peu : l'air se contracte avec le froid.
➤ Cela peut affecter la flottabilité.

3. Risques liés aux équipements en eau froide

Le givre peut se former sur les détendeurs à cause de la baisse de température provoquée par la détente de l'air (lois combinées des gaz).
➤ Comprendre la relation entre température et volume/pression aide à mieux anticiper ces problèmes.

📌 En résumé

Élément	Impact de la loi de Charles
Remplissage de la bouteille	Pression diminue en refroidissant
Gilet stabilisateur en eau froide	Volume d'air diminue, flottabilité change
Prévention du givrage	Température baisse → comprendre les risques