Why Do PCR Machines and Refrigerated Centrifuges Need to Be Turned Off with the Lids Open?

Think about the common PCR machines and refrigerated centrifuges you use in the lab. When they are turned off, are their lids usually open? Here’s why.

Understanding the Equipment

1. PCR Machines and Heated Lids

Modern PCR machines have a “heated lid” function. This lid heats the top of the sample tubes, separate from the heating at the bottom. The lid’s temperature is typically higher than the block’s temperature.

The heated lid prevents condensation. When the PCR reaction liquid heats up, it creates steam. This steam would condense on the cooler lid. The heated lid stops this condensation, which keeps the reaction volume from changing and affecting your results. After the PCR process, the final step often holds the samples at 4°C for a long time. This gives the samples a continuous cold environment to protect their biological activity if you forget to remove them immediately.

2. Refrigerated Centrifuges

The main purpose of a refrigerated centrifuge is to keep samples cold during centrifugation. This is important for samples that need a low-temperature environment. The common low temperature for this is also 4°C.

The Role of Temperature Differences

Both types of instruments have a cooling system. This creates a temperature difference between the inside of the machine and the outside air. When moisture in the air meets a colder surface, it turns into small water droplets, creating condensation.

When a PCR machine or refrigerated centrifuge finishes a run, its final temperature is often 4°C. The warmer, ambient air then comes in contact with the colder interior of the device. This causes the moisture in the air to condense into small water droplets that stick to the inside of the instrument.

Leaving the lid open after turning off the machine allows these water droplets to evaporate slowly. If you don’t, you will find a lot of condensation inside the machine the next time you open the lid. This is especially true for centrifuges, since PCR machines have some residual heat from the heated lid that helps with drying.

Wiping away this condensation is extra work and takes time. More importantly, it can cause the instrument to rust. Therefore, any lab equipment that finishes its work in a low-temperature state should be turned off with the lid open.

To understand the fundamental principles common to all types of PCR, be sure to read our main article: What is PCR & How does PCR work?.

This guide is maintained by HINOTEK’s core technical team, comprised of senior engineers and application scientists with over two decades of hands-on experience in fields such as microscopy, centrifugation, and spectrophotometry. We are committed to ensuring that every piece of information in this guide—from instrument principles and technical specifications to laboratory procurement advice—maintains the highest level of accuracy and timeliness.
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