Online Heat Stress Weather Station

TWL-1SV is the advanced heat safety solution with remote heat management capabilities. Using TWL and WBGT algorithms, it calculates heat stress indices from ambient temperature, humidity, radiant heat, wind speed, and direction. Real-time data can be viewed and downloaded on Scarlet heat monitoring web portal remotely. Users can receive instant heat alerts via browser or email, ensuring proactive safety measures.

Heat Monitoring

TWL-1SV collects heat measurements and connects via ethernet to provide real-time data and visual alerts directly to the Scarlet online heat monitoring portal. The web portal enables you to monitor multiple TWL-1SV stations, ensuring comprehensive heat management.
thermal meter

Weather Station for Heat Monitoring

thermal meter
thermal meter
thermal meter

Online Heat
Safety Solution

Everyone can easily access heat data and alerts through Scarlet web portal from anywhere. On-site officers can check updates on their tablets and smartphones, while office team members can monitor from their PCs.

Efficient Heat Management

Continuous Data
Update thermal work limit values in every 2-min and present TWL recommendation in tables or charts.
Dynamic calculations thermal work limit (TWL), wet bulb globe temperature (WBGT), and tracking heat index (HI).
Alert Status
Receive TWL alerts from all TWL-1SV stations on your display, regardless of location.

Visual Alerts

Based on TWL values, it alerts of heat risks at worksites with color codes—red (high risk), yellow (medium), and green (low). The alerts include a hydration plan and are accessible via email and web browser. This helps prevent heat-related illnesses, ensuring effective safety management.

Why Thermal Work
Limit (TWL) Alerts?

Getting TWL alerts is crucial for maintaining workplace safety in heat-intensive area. It informs if the worksite is in high (TWL< 115), medium (115 < TWL < 140), or low risk (TWL>140) conditions for workers to work. By receiving immediate notifications of TWL changes, managers can take adjustment of work conditions, ensuring a safe and productive environment.

Feed Crucial Data to
Your Existing Systems

Effortlessly integrate crucial data into your existing system using RS232/Modbus connectivity. Enhance system functionality and decision-making by seamlessly feeding real-time data for comprehensive analysis and improved operations.
thermal meter

Portable Heat Stress Meter - TWL-1S

TWL-1S is a portable heat stress meter designed to measure WBGT and TWL heat indices on-site. This compact device provides you with instructions for work, rest, and hydration plans. The user-friendly interface is shown in tri-colors backlight with information to alert HSE managers if the environment is safe for workers to work.

Integrable with Your Devices & More Environmental Sensors

Get real-time data access with MODBUS RTP through an RS232 interface. Customize your solutions with features like large signage, warning lights, and sirens.
TWL-1SV can be integrated to display real-time heat-related indices on outdoor signs for increased awareness and safety, ensuring heat-related indices are visible in any environment.
Warning Devices
TWL-1SV can be connected to warning devices such as siren or alarm, to ensure heat-risk alert is visible in any environment.
More weather sensors available
Extend your weather data collection with supplementary sensors like rainfall and light intensity gauges.
thermal meter

Protect Workers from Heat-Related Illnesses

Extreme hot weather can put workers at risk of heat-related illness, injury or even death in extreme cases. Some of the illness includes heat exhaustion, heat cramps, or heat rashes, and heat stroke. The effective way to manage heat stress in the work place is to first by determining the heat index level.

Where does Scarlet TWL-1SV Apply

Tower Cranes
Port Terminal
Chemical Plant
Outdoor Event
Construction site


thermal meter IoT
  • Thermal Work Limit (TWL)
  • Wet Bulb Globe Temperature (WBGT)
  • Heat Index (HI)
  • Globe Temperature
  • Dry Bulb Temperature
  • Wet Bulb Temperature
  • Humidity
  • Wind Speed
  • Wind Direction
TWL CalculationBased on Tw, Tg, Ta and WS
WBGT Calculation0.7 x Tw + 0.2 x Tg + 0.1 x Ta
Heat index (HI)21 to 45 °C
Globe thermometer (Tg)Range: 0 to 80 °C /
Accuracy: ±1.5 °C (15 to 40 °C); ±2.0 °C (others)
Dry-bulb temperature (Ta)Range: -40 to 80 °C / Accuracy: ±0.5 °C
Wet-bulb temperature (Tw) calculation0 to 66 °C
HumidityRange: 0 to 100 % RH / Accuracy: ±2%
Wind speed (WS)Range: 0 to 40 m/s / Accuracy: ±5%
Power supply / consumptionRange: 0 to 359° (no blank sector) / Accuracy: ±3°
MemoryBuild-in SD card (Backup storage for cloud connection lost)
Material casingAluminum

The TWL-1S has been tested and validated by Health Authority – Abu Dhabi in the extreme high temperature and high humidity Gulf region as well as the mines in Australia. The TWL algorithm used by TWL-1S device is the latest version attested by the research team in Curtin University, Australia.


Risk assessment for heat-related illness in the worksite is quite essential in high temperature environments. TWL-1S can be applied at outdoor and indoor working environments. For instance, a health and safety officer can place the TWL-1S at the “hot spot” zone in worksite and continuously monitor environmental parameters. With 200 meters transmission distance of wireless signal, the paging system can actively warn safety officers in real time. TWL-1S is able to help managers set work/rest cycle and hydration plans for workers.

As TWL is to mimic the effects of the working environment on laborers, it is suggested the TWL-1S unit should be placed on the worksite where the majority of workers are located. For example, if there is no shade provided on the worksite, the TWL-1S should be exposed to sunlight as most workers are.

However, in order to prolong the machine life, you can place TWL-1S under sunlight while measuring. Before pushing the TWL button, please allow TWL-1S at least 10 minutes in the working environment to get balance. After the TWL level shows up, you can put it back to shade.

The TWL is the thermal work limit. It’s an advanced heat stress index and research found it more useful in workplaces.

The TWL predicts the maximum level of work that can be carried out in a given environment, without workers exceeding a safe core body temperature 38.2 °C (100.8 °F) and sweat rate (< 1.2 kg or 2.6 lb per hour). WBGT does not incorporate a direct measure of wind speed and requires estimation of metabolic rates, which can have a margin of error up to 50%. Heat stress indexes such as WBGT and ISO 7933 do not take into account the effects of long hours of hard work, dehydration, or the impact of personal protective clothing and equipment. WBGT and heat index are too conservative and inappropriate for practical in the extreme working environments such as Middle East countries or high-temperature process industry or mines. Scarlet TWL-1S incorporated both WBGT and TWL index features. You can simply switch heat indices for your need.

Our Customers

What Our Clients Say

TWL-1S’s friendly user interface has assisted me a lot in implementing the new occupational heat exposure prevention system in the field. This is one of the key elements to success.

Dr. Sanad Al Sanadi, Occupational Health Team Leader, ADMA-OPCO

Since Commencing the heat stress management program in November 2013, the project has not had a SINGLE CASE of a heat stress related illness despite air temperatures of 45 degrees.

Simon Lewis, Project Manager, Leighton Contractors Australia

Companies in Abu Dhabi should comply with EHSMS heat safety standards by adopting thermal work limit (TWL) for risk assessment of heat working environment.

Eng. Ibrahim Khalid, HSE engineer, Abu Dhabi Municipality HSE Division
Heat Stress Meter-TWL-1SV

Thank you for the interest in TWL-1SV. Please fill out the form below. We will get back to you in few hours.