Manufacturing or Formulation and Filling of Aerosols

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Aerosol Manufacturing Process

Manufacturing of aerosols are done at two stages.

Manufacturing of aerosols- stages

The manufactured aerosols can be filled in to the containers can be done by following methods and apparatus used.

a) Cold filling Apparatus

b) Pressure filling apparatus

c) Compressed gas filling apparatus

d) Rotary filling machine

a) Cold filling apparatus1: Cold filling apparatus consists of an insulated box which fitted with copper tubings and filled with dry ice or acetone. The fitted copper tubings increase the surface area and cause faster cooling. The hydrocarbon propellant is not to be stored in the copper tubings as it might cause explosion.

Cold filling apparatus - Aerosols

b) Pressure filling apparatus1: Pressure filling apparatus consists of a metering burette capable of measuring the amount of propellant to be filled to the container. The mixture of propellant or propellant/s are added through the inlet valve present to the bottom of the valve under its own vapour pressure. A cylinder of nitrogen or compressed gas is attached to the top of the valve and the pressure of nitrogen causes the propellant to flow to the container through the metering burette. The propellant flows to the container stops when the pressure of the flowing propellant becomes equal to the pressure of the container.

Aerosols- Pressure filling Machine

Aerosols- Table top aerosol filling

c) Compressed gas filling apparatus1: A compressed gas propellant is used. As the compressed gas is under high pressure, so the pressure is reduced by pressure reducing valve. A pressure of 150 pounds per square inch gauge is required to fill the compressed gas propellant in the aerosol container. The product concentrate is placed in the pressure gauge and the valve is crimped in its place. The air is evacuated. The filling head is inserted into the valve opening. Upon the depression of the valve, the compressed gas propellant is allowed to flow into the container. The compressed gas stops flowing when the pressure of the compressed gas flowing to the container from the burette becomes equal to the pressure within the container. In case of increasing the solubility of the gas in the product concentrate and also when an increased amount of compressed gas is required, carbon dioxide and Nitrous dioxide is used. The container is needed to be shaken during and after the filling operation to enhance the solubility of the gas in the product concentrate.

Aerosols- Compressed gas filling

Cold filling method:
Two different methods are involved:The aerosol product is filled into the container is by two methods:

  • In the first method, the product concentrates are chilled to a temperature of - 30 to - 400 F. The chilled product concentrates are added to the chilled aerosol container. The chilled propellant is added through an inlet valve present under side of the valve of the aerosol container.
  • In the second method, both the product concentrate and the propellant are chilled to - 30 to - 400 F. Then the mixture is added to the chilled container.

In both the above methods, after the aerosol containers are filled, the valves are set in its place and the filled aerosol containers are passed through a water bath in which the contents of the containers are heated to 130 0F to test for leaks and strength. After checking the containers apply air drying, cap it and label it.

Cold filling method is advantageous for the filling of metering valve containing aerosol container. The pressure filling method is more prominent than cold filling method as most of the formulations cannot be cooled to very low temperatures.

Aerosols- Cold filling process and Machine used for Cold Filling

Pressure filling method:

The product concentrate is filled to the aerosol container through the metering pressure filling burette at room temperature. The propellant is added through the inlet valve located at the base of the valve or under the valve after the crimping of valve. The flow of propellant to the aerosol container continues till the pressure of the filling propellant becomes equal to the pressure within the container. The aerosol container are capped and labeled.

A. Method-1

- The product concentrate is added to container at room temperature.

- The valve crimped into place.

- The propellant is then added under pressure through the valve stern or through the actuator and around the sealing gaskets.

B. Method-2

- Under the cap method: product concentrate is added to the container and valve place in a position.

- A seal is formed around the shoulder of the container and using a vacuum, the valve cup is raised slightly from the can and propellant is added.

- The valve is then crimped into the place.

This method is more prominent than cold filling method as most of the formulations cannot be cooled to very low temperatures.

Rotary filling machine: The pressure filling method is first slower than cold filling method. With the development of newer technique the speed of pressure filling method was increased. The concentrate is added to the container at room temperature, and the valve is crimped in place. The propellant is added through the valve or "under the cap". Since the vacuum contains extremely small openings (0.018 to 0.030 inches), this step is slow and limits production. With the development of new rotary filling machines for aerosols and newer filling heads, which allows propellant to be added around and through the valve stem.

Advantages of the pressure filling methods compared with cold filling method:

  • The emulsions or suspensions are unstable at very low temperature. At that time the pressure filling method is the preferred method then that of cold filling method.
  • Here the absence of moisture reduces the chance of contamination.
  • The rate of production is high.
  • Propellant loss is low.

Compressed gases filling:

Here, when the compressed gases are used as the propellant in aerosol systems, the compressed gas is transferred from large steel cylinders into the aerosol containers. Before filling, the product concentrate is placed in the container, then the valve assembly is crimped into place and the air is removed from the container by a vacuum pump.

The compressed gas is then passed into the container through a pressure reducing valve attached to the gas cylinder; when the pressure within the aerosol container is equal to the predetermined rate and setted/ regulated delivery pressure, the stops gas flow and the aerosol valve is restored to the closed position. Some gases like carbon dioxide and nitrous oxide (which are slightly soluble in the product concentrate) the container is manually or mechanically shaken during the filling operation to achieve the desired pressure in the head space of the aerosol container.

For large scale of production Concentrate filler, Valve placer, Purger and vacuum crimper, Pressure filler, Leak test tank equipments are used.

Testing the Filled Containers:

  • After filling by either of method, the aerosol container is tested under different environmental conditions for leaksor weaknessin the valve assembly or container.
  • Proper functionof the valve should be tested for filled aerosol containers.
  • The valve discharge rateis determined by discharging a portion of the contents of a previously weighed aerosol during a filling period and calculating by the difference in weight in grams of contents discharged per unit of time.
  • Aerosols tested for their spray patterns for particle size distribution of the spray and for accuracy and reproducibility of dosage when using metered valves.

Packaging, Labeling and Storage

  • A unique aspect of pharmaceutical aerosols compared to other dosage forms is that the product is actually packaged as part of the manufacturing process. The product is completely manufactured before itself and then placed in the appropriate container.
  • Most aerosol products have a protective cap or cover that fits snugly over the valve and mounting cup. This mounting cap protects the valve against contamination with dust and dirt. The mounting cap, which is generally made of plastic or metal and also serves a decorative function.
  • Aerosols containers should be maintained with the protective caps in place to prevent accidental activation of the valve assembly or contamination by dust and other foreign contents or atmospheric contents.
  • Therapeutic aerosols that are to be dispensed only with prescription and generally labeled by the manufacturer with plastic peel-away labels or easily removed paper labels, so that the pharmacist easily replace the manufacturer's label.
  • Safety and precaution labels must warn users not to puncture pressurized containers and not to use or store them near heat/temperature or an open flame and not to incinerate them.
  • Exposure to temperatures above49degC (120degF) may burst an aerosol container.
  • When the canisters are cold (less than the usual results into spray). This may be particularly important to users of metered-dose inhalation sprays.
  • For aerosol products are generally recommended for storage between 15degC and 30degC (59degF and 86degF).

Typical label of Aerosols 12



PRODUCT 'X' 200ml

This tells you what the product is, and how much is in the container.


This tells you that this section of the label contains the safety information.

Do not spray or use directly onto food preparation surfaces, fabrics, or polished surfaces

This is because the product may taint food, might stain fabrics, or may affect the appearance of polished surfaces.

Do not spray on or near naked flames, including cooker pilot lights and fires

This will reflect that the product has a 'flammable' classification.

Don't use on floors, the inside of baths or shower trays, as the high gloss could be dangerous

This is often seen on aerosol polishes, and is a good example of safety information.


This section contains statutory and other recommended wording.

Use formulation only as directed. Intentional misuse by inhaling the contents can be harmful or fatal.

This is a BAMA recommendation, and has been superseded by:-


The BAMA recommendation of July 1997 for the labeling of all UK aerosols.

Pressurized container

This is a statutory requirement.
This tells you that the contents of the container are under pressure, and the aerosol is different from other packages.

Protect from sun light and do not expose to temperatures exceeding 50degC. Do not pierce or burn after use.

This is a statutory requirement. During manu-facture aerosols are tested at 50degC, however if exposed to higher temperatures there is a risk that the container may eventually burst.



Don't use spray on a naked flame, onto or near fire, or any incandescent material.
Keep away from sources of ignition - No smoking

This is a statutory requirement.

Flammable or
Extremely flammable or together with a flame symbol or
X% by mass of the contents are flammable

This is a statutory requirement, and reflects the flammability classification of the product.


A statutory requirement.

About the Author

Naseeb Basha Shaik's picture

Working as Assistant Professor, Pharmaceutics Department at G.Pulla Reddy College of Pharmacy, Mehdipatnam, Hyderabad.

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