It’s safe enough, in the Finnish army we occasionally get the tent heater red hot, and as long as nothing flammable touches it or is too close, it’s fine. It will radiate heat quite well when that hot, but won’t be anywhere close to dangerous if you know what you’re doing. In the tent we of course have some water nearby to extinguish the possible flames but still.
You basically need to have it glowing red if you’re to keep the tent warm in -15 °C or lower. - 30°C needs something closely resembling the picture posted.