it's about Aerosol. This slide made by Sunayan.

1. Aerosol
Introduction:-
An aerosol is a colloid of fine solid particles or liquid droplets, in air or
another gas.Aerosols can be natural or artificial. Examples of natural aerosols
are fog, forest exudates and geyser steam. Examples of artificial aerosols are
haze, dust, particulate air pollutants and smoke. The liquid or solid particles
have diameter mostly smaller than 1 ?m or so; larger particles with a
significant settling speed make the mixture a suspension, but the distinction is
not clear-cut. In general conversation, aerosol usually refers to an aerosol
spray that delivers a consumer product from a can or similar container. Other
technological applications of aerosols include dispersal of pesticides, medical
treatment of respiratory illnesses, and combustion technology. Diseases can also
spread by means of small droplets in the breath, also called aerosols.
Definitions:-
An aerosol is defined as a colloidal system of solid or liquid particles in a
gas. An aerosol includes both the particles and the suspending gas, which is
usually air.
Aerosoles are products that are packaged under pressure and contain
theraputically active ingredients that are released upon activation of an
appropriate valve system.
Aerosole characteristics:-
* Particale size distribution.
*Uniformity of dose for metered valve.
*Delivery rate.
*Wetness and temperature of the spray.
*Spray pattern.
*Velocity of spray.
*Fluid viscosity.
Advantages:-
A dose can be removed with out contamination of materials.
The medication can be delivered directly to the affected area in a desired form,
such as spray, steam, quick breaking foam or stable foam.
irritation produced by the mechanucal application of topical medication is
reduced or eliminated.
Ease of convenience of application.
Application of medication in thin layer.
Disadvantages of Aerosols:-
*Expensive
*Chlorofluorocarbon propellants cause Ozone layer depletion.
*Inflammability
*Toxicity
*Explosivity
Component of Aerosol:-
*Propellant
*Container
*Valve and actuator
*Product concentrate
Formulation Development of Aerosole:-
What exactly is a pharmacutical aerosole? A pharmacutical aerosol in a general
way can be defined as an aerosol product containing theraputically active
ingredients dissolved, suspended or emulsified in a propellant or mixture of
solvant and propellant and intended for oral or topical administration or for
administration into body orifices.
Manufacturing of Pharmacutical Aerosol:-
Apparatus
*Pressure filling apparatus
*Cold filling apparatus

2. *Compressed gas filling apparatus
Types of Aerosol system:-
*Solution system
*Water based system
*Suspention or Dispersion system
*Foam systems
1. Aqueous stable foams
2. Non aqueous stable foams
3. Quick-breaking foams
4. Thermal foams
* Intranasal aerosols
Aerosol Devices:-
*Dry Powder Inhalers (DPI)
*Metered Dose Inhaler (MDI)
*Nebulisers
Coagulation:
As particles and droplets in an aerosol collide with one another, they may
undergo coalescence or aggregation. This process leads to a change in the
aerosol particle-size distribution, with the mode increasing in diameter as
total number of particles decreases.[26] On occasion, particles may shatter
apart into numerous smaller particles; however, this process usually occurs
primarily in particles too large for consideration as aerosols.
Effects of Aerosols:-
Volcanic eruptions release large amounts of sulphuric acid, hydrogen sulphide
and hydrochloric acid into the atmosphere. These gases represent aerosols and
eventually return to earth as acid rain, having a number of adverse effects on
the environment and human life.
Aerosols interact with the Earth's energy budget in two ways, directly and
indirectly.
E.g., a direct effect is that aerosols scatter sunlight directly back into
space. This can lead to a significant decrease in the temperature, being an
additional element to the greenhouse effect and therefore contributing to the
global climate change.
The indirect effects refer to the aerosols interfering with formations that
interact directly with radiation. For example, they are able to modify the size
of the cloud particles in the lower atmosphere, thereby changing the way clouds
reflect and absorb light and therefore modifying the Earth's energy budget.
When aerosols absorb pollutants, it facilitates the deposition of pollutants to
the surface of the earth as well as to bodies of water.This has the potential to
be damaging to both the environment and human health.
Aerosol particles with an effective diameter smaller than 10 ?m can enter the
bronchi, while the ones with an effective diameter smaller than 2.5 ?m can enter
as far as the gas exchange region in the lungs, which can be hazardous to human
health.
Aerosol propellants
If aerosol cans were simply filled with compressed gas, it would either need to
be at a dangerously high pressure and require special pressure vessel design
(like in gas cylinders), or the amount of payload in the can would be small, and
rapidly deplete. Usually the gas is the vapor of a liquid with boiling point
slightly lower than room temperature. This means that inside the pressurized
can, the vapor can exist in equilibrium with its bulk liquid at a pressure that
is higher than atmospheric pressure (and able to expel the payload), but not
dangerously high. As gas escapes, it is immediately replaced by evaporating
liquid. Since the propellant exists in liquid form in the can, it should be
miscible with the payload or dissolved in the payload. In gas dusters, the
propellant itself acts as the payload. The propellant in a gas duster can is not
"compressed air" as sometimes assumed, but usually a haloalkane.
Conclution:-
* At present there is much interest in developing MDIs for conditions including
asthma, COPD, Chronic bronchitis, emphysema and other respiratory diseases etc.

3. *Many of compounds have been developed using biotechnology process and their
delivery to the respiratory system via MDI in an extremely challenging
undertaking.
* As Chlorofluorocarbon (CFC) propellants cause ozone depletion, they are being
replaced with acceptable Hydro fluoro carbons (HFC) propellants.
Refarances:-
1. https://en.wikipedia.org/wiki/Aerosol
2. https://www.slideshare.net/sufpharmacist/aerosols-18373102
3. https://en.wikipedia.org/wiki/Acid_rain#Adverse_effects