Prior to fighting any fire with a portable fire extinguisher, several important factors should be taken into account:

1. Fire Size and Containment: Ensure the fire is small, contained (such as in a waste basket), and limited in size. It should be in its incipient or beginning stage and not spreading. The flames should not be higher than the firefighter's head.
2. Knowledge of the Fire Type: Know what combustible material is burning. Use only the correct type of extinguisher for that fire.
3. Evacuation Path: Have a clear and safe evacuation path behind you. If the fire grows or becomes uncontrollable, you must be able to evacuate immediately.
4. Air Safety: Check if the air is safe to breathe and does not contain large amounts of toxic smoke or gases that would require respiratory protection.
5. Heat and Smoke: Make sure the environment is not too hot or smoky to approach the fire safely.
6. Proper Training and Equipment: Only attempt to use a fire extinguisher if you are trained in its use, know how to operate it correctly, and have the appropriate extinguisher for the fire.
7. Limited Extinguishing Agent: Be aware that portable extinguishers contain a limited amount of agent, usually allowing only about 10 seconds of use.
8. Alert Others: Sound the fire alarm and call emergency services before attempting to fight the fire.

If any of these conditions are not met, evacuation is the safer choice.