Can Thermal Scopes See Through Smoke, Glass or Walls?

Did you know that firefighters use thermal scopes to save lives? But are they that useful with all the smoke? 

Many people who enter the thermal world actually end up asking this question: can thermal scopes see through smoke?

And the short answer is yes. The long answer is a bit more complicated, though.

We’ll first break it down and get into more detail below, but we’ll also cover other common objects that allow or hinder thermal scopes from seeing through them to give you a better idea of how to utilize your thermal device best.

What Can You See With a Thermal Scope?

Simply put, what you can see with a thermal scope are hot and cold spots. 

Thermal scopes don’t use visible light, like humans and most animals. Instead, thermal scopes see the heat coming off objects and living things. The electronics inside the scope then convert this into an image people can see.

If the temperature of what you’re looking at is exactly the same across, you won’t pick out any detail, as details in a thermal image come from temperature differences that can range from tiny to big.

In this image, the hottest part of the hog just over the chest is nearly white. The tips of the ears are the coldest and show up purple. Because the ground is almost the same temperature, you won’t pick out many details.

The most common thermal image will show the very coldest parts as black. As temperatures increase, the colors move from blue to red to yellow and finally white for the hottest. Some thermal scopes, however, let you change the color scheme. (2)

Can thermal scopes see through smoke?

Yes, thermal scopes can see through smoke. Particles in the smoke block visible light but allow heat signatures to penetrate. In fact, firefighters use thermal scopes for this very reason. With it, they can find flames, hot spots, and even living creatures the smoke is hiding.

However, this is not a guarantee for seeing through copious amounts of smoke. 

Smoke is made of heated particles and has to be created by something hot. If the heat source making the smoke is close, the thermal scope may pick up that heat and therefore not see very clearly through the smoke. (1)

Can thermal scope see through glass and windows? 

Generally, thermal scopes can’t see through glass because it’s a very good insulator. If you focus a scope on a piece of glass, it’ll pick up the heat reflected off it.

You can even try this out yourself. So, stand behind a sheet of glass and put a hand on the pane, then leave it there for a minute or two. If someone else looks at the glass through a thermal scope, they’ll see the heat signature left by your hand. 

The scope won’t be able to see you behind the glass. Any part of you that is not behind the glass can be seen. 

Roswell Flight Test Crew shows this perfectly in the video below. When the speaker holds up a pane of glass, on the regular camera, he is completely visible. But in the thermal camera view, everything behind the glass is just a dark square.

Can thermal scope see through trees?

No, thermal scopes can’t see through trees as they’re too thick to allow heat to pass through. But they can see whatever is on each side of the tree. 

On the other hand, thermal devices can see through brush to a limited extent. However, if the brush is thick, the scope won’t see the heat sources through it.

The ability to see through bushes is one thing that makes thermal scopes so effective for varmint hunters. A coyote, for example, can’t crouch down behind a bush to hide from potential prey – with a thermal, the song dog will likely be detectable.

Can thermal scope see through walls or concrete?

Nope, thermal scopes can’t see through walls or concrete. The idea that a thermal scope can see through a door or a wall is Hollywood movie fiction. 

Wood and most wall materials are excellent insulators, and that’s why so many cooking tools are either made from wood or have wood handles — no heat transfer.

The scope may pick up a heat signature that either has to be very hot or stay in one place long enough for a heat transfer to occur.

Concrete is an even better barrier to heat transmission. Don’t count on thermal scopes to see through concrete. If a scope picks up a heat signature from the other side of concrete, the heat source has stayed put for a long time.

Can thermal scopes see through fog?

Yes, thermal scopes can see through fog as it doesn’t hold as much heat as smoke. Fog is a poor insulator, as the water vapor will let heat signals pass through to a great degree. 

However, fog will limit a thermal’s effectiveness at long distances.

Can thermal scopes see through metal?

Thermal scopes can’t see through metal but can pick up heat transmitted through it. 

You can place your hand on a sheet of roofing tin for a minute, and a thermal will see the heat impression of your hand on the other side. After you move your hand, the scope will continue to see the heat signature until that part of the metal reaches the same temperature as the rest.

Can thermal scopes see through plastic or aluminum foil?

A thermal scope’s ability to see through plastic depends on the material’s thickness. 

If it’s a single sheet of thin plastic wrap, like that used to cover a dish of food, then yes. If it’s a single-ply garbage bag, also yes, but with a bit less resolution than the food wrapper, as garbage bags are made of thicker plastic and insulate better.

However, thermal devices can’t see through thick plastic because the insulation rating is too high.

Similarly, thermal scopes can’t see through aluminum foil. It’s an excellent insulator, which makes it really helpful when sighting in a thermal rifle scope during the day. If you post pieces of foil on a target, they’ll stand out from the rest and be perfect for sighting in.

Can you see snakes with thermal imaging?

Generally, no, you can’t see snakes with thermal. Snakes are reptiles and cold-blooded, which means their body temperature is the same as their surroundings. 

If a snake is resting on the ground, its body temperature will be the same as the ground. That means the thermal sensor will see the ground and the snake at the same temperature.

Can you see deer antlers with thermal imaging?

Sometimes, yes, you can see deer antlers with thermal.

When deer are in velvet, the blood flowing to the growing bones makes the antlers stand out because they’re warmer than the air around them.

After the deer sheds the velvet, the bare bones quickly cool to the ambient temperature. Antlers close to the head may be warmer because of transmitted body heat, but that isn’t enough to tell you how many points the deer has.

Thermal Scopes For Hog Hunting

For their ability to see heat at such long ranges, thermal scopes have become very popular for hunting, particularly for hog hunting. If you’re a hunter looking for more info, check out our article on the top thermal rifle scope for hog hunting.

Reference

1. Science Friday, Thermal Imaging Technology Helps Firefighters See Through Smoke, retrieved from https://www.sciencefriday.com/segments/thermal-imaging-smoke/
2. Teledyne Flir, How Do Thermal Cameras Work, retrieved from https://www.flir.com/discover/rd-science/how-do-thermal-cameras-work/