Hot Air Oven
An electrically heated, insulated cabinet that holds samples or glassware at a set temperature. In QC it is used mainly for loss on drying, drying of reference materials and drying of glassware.
- Pharmaceutical
- Food & beverage
- Chemicals
- Materials testing
- Education
Test your Hot air oven knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. What is the most common QC use of a hot air oven?
basicQ2. Loss on drying measures:
basicQ3. After drying, the weighing bottle should be:
basicQ4. What is the purpose of temperature mapping of an oven?
intermediateQ5. A sample bottle weighs 26.4398 g before drying and 26.4360 g after. The empty bottle weighs 25.4312 g. What is the LOD?
intermediateQ6. What does 'dried to constant weight' mean?
intermediateQ7. A substance decomposes at 105 °C. How is its LOD usually determined?
advancedQ8. Which item is NOT appropriate to place in a standard (non-explosion-proof) hot air oven?
advanced
Viva questions
Think of your answer first, then open it to compare.
1. What is the difference between temperature accuracy and temperature uniformity?
Accuracy is how close the chamber temperature at a reference point is to the set point. Uniformity is how much the temperature varies between different positions in the chamber. An oven can be accurate at the centre but still have hot and cold spots.
2. Why is the stopper removed from the weighing bottle during drying but replaced before cooling?
Removing it lets volatiles escape during drying. Replacing it before taking the bottle out stops the dried sample from picking up moisture from the air while it cools and is weighed.
3. What is the difference between natural and forced convection ovens?
Natural convection ovens rely on warm air rising and give gentle air movement, useful for light powders. Forced convection ovens use a fan for faster heating, quicker recovery after door opening and better uniformity.
4. What would you check during OQ of a hot air oven?
Controller and display accuracy against a traceable thermometer, empty-chamber temperature mapping at the working set points, heat-up time, recovery after door opening, alarm and over-temperature cut-out function, and timer function if used.
Keep every Hot air oven in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.