There are cleaning solutions that are not advisable to be used with an ultrasonic cleaner. These are solutions that can cause harmful situations if used in ultrasonic cleaning. Solutions that are flammable, such as acids, should be avoided. Heat is very important in ultrasonic cleaning. The temperature inside the cleaner is increased during the cleaning process. Also, the implosion of cavitation bubbles produce heat. Therefore, using cleaning solutions that ignite easily can cause accidents. Corrosive substances, such as bleach, should also be avoided. If an acid or bleach is still chosen as an ultrasonic cleaning solution, it should be used in indirect cleaning. This means putting the solution in another container, such as a beaker.