Historically CFCs (Chlorofluorocarbons e.g. CFC 11, CFC 12 & CFC 114) were used in medical aerosol applications as they are non-flammable, chemically inert and virtually non-toxic. However, CFCs are controlled substances and have largely been phased out under the Montreal Protocol due to their ozone depleting properties. Hydrofluoroalkanes (HFAs e.g. HFA 134a and HFA 227ea) have proved to be the ideal solution as they have similar physical, flammability, toxicity and thermodynamic properties to the CFCs they have replaced but do not deplete the Ozone Layer.
Pharmaceutical companies use the term “HFAs,” whereas the other industries, such as Refrigeration and Air Conditioning industry use the term “HFCs” (hydrofluorocarbons) to describe the same substances.
The switch from CFCs to HFAs for metered dose inhalers (MDIs) has taken about 15 years due to the need to ensure that each active drug formulation is stable and meets the specific medical requirements. This has been a major undertaking by the pharmaceutical companies and is finally being completed globally.
A clear distinction must be made between medical aerosols, which are essential for patient’s health, and industrial aerosols. The CFC and HFA propellants are excipients used in medical aerosols to administer the active ingredient directly tothe patient and, as such, must:
- Have ultra high purity
- Pass rigorous testing and quality control
- Be manufactured in dedicated facilities according to continuous Good Manufacturing Practices (GMPs)
- Metered dose inhalers
- Oral, nasal and other topical sprays
These medical aerosol products are extremely important, e.g. metered dose inhalers are used extensively for the treatment of asthma and chronic obstructive pulmonary diseases (COPD).
HFCs used are used in firefighting situations due to their beneficial chemical and physical fire extinguishing properties. They have low toxicity, are non-conductive, clean agents and, therefore, leave no residue.
HFCs, mainly HFC 227ea and HFC 23, have been used to replace Halons (e.g. Halon 1301 and Halon 1211), which are controlled, and have largely been phased out under the Montreal Protocol due to their ozone depleting properties.
The current use of HFCs in fire protection applications is limited to those cases where safety, speed and space are critical. Most HFCs fire fighting applications are installed where conventional extinguishing agents, such as carbon dioxide, water or dry powder, are unsuitable. This would include the need to extinguish a fire without damage to sensitive equipment, as found in computer rooms, clean rooms, museums, and data processing centers.