Construction projects don’t stop because the temperature gets cold. It’s crucial to keep a project moving and temporary heaters can be an asset for staying on schedule. They are particularly beneficial in the winter months for thawing ground, curing concrete, and general drying/warming purposes. However, while temporary heaters are helpful, they can quickly become hazardous, and potentially lead to fire if improperly installed.
Fires are the main reason to take temporary heater safety precautions. Unvented and self-contained heaters are used most often on jobsites. Proper venting, is an important consideration when using temporary heaters. Additionally, improper installation and clearance are the main causes of accidents.
OSHA Requirements for Temporary Heaters
According to OSHA (1926.154), when implementing a temporary heating device, there are five standards that one must adhere to:
- Ventilation. Fresh air or mechanical ventilation must be provided for safety, proper combustion, and temperature management.
- Clearance and mounting.
- At a minimum, circulating heaters must be placed 12″ from a room’s sides and rear, and 18″ from its chimney connector.
- Radiant heaters must be placed at least 36″ from a room’s sides and rear, and 18″ from its chimney connector. Temporary heaters with shorter clearances may be installed accordingly.
- Heaters which are not safe for direct placement on the floor must rest on heat-insulating material, at least 1 in. of concrete, or its equivalent. The heat-insulating material must extend 2 ft. beyond the heater in all directions.
- Heaters must be located at least 10 ft. from any coverings (ex. tarpaulins, canvas) and these coverings must be severely fastened to avoid becoming ignited or knocking away the heater.
- Stability. Unless the manufacturer’s markings permit otherwise, heaters in use must be set horizontally level.
- Solid fuel salamanders. Solid fuel salamanders are prohibited in buildings and on scaffolds.
- Oil-fired heaters. Flammable, liquid-fired heaters must have a primary safety control, neither barometric or gravity oil feed, that stops fuel in the event of flame failure. Barometric or gravity oil feed heaters can only be used with integral tanks. Heaters used with separate supply tanks can be directly connected for gravity feed, or an automatic pump, from a supply tank.
Choosing a Portable Heater
There are a few different types of temporary heaters to choose from:
- Electric Heaters
- Direct Fired Heaters
- Indirect Fired Heaters
Let’s talk about the benefits and hazards of each type.
Electric heaters are quiet and clean. They can be used both indoors and outdoors. Because there’s no combustion, there’s no need for additional ventilation making this a safe choice. Electric heaters don’t add to the humidity levels, so they can be used for dry out applications, such as concrete curing. Electric heaters come in many sizes to fit your needs, provided you have the electrical power needed. Most units require at least 208V. Some are equipped with thermostats giving you a level of control over the amount of heat generated.
As with all portable heaters, you’ll need to take care in where you set it up, allowing for proper clearances and away from combustible materials. Ensure the electrical output is enough for the heater you’re using. Inspect the power cords, plugs, and other safety features prior to use. Never use a unit that appears to be damaged. Look for units that have an auto-shut-off feature if unit gets knocked over or overheats. Electric heaters should not be used in areas that are or could become wet.
Direct Fired Heaters
A direct fired heater uses propane, natural gas or diesel fuel to heat the space. In these systems, air is forced directly through a flame providing direct heat. These types of heaters are great for large spaces such as warehouses or large construction sites. A high amount of heat can be generated with a small unit, and they are more fuel-efficient than their indirect-fired cousin. These units also have built-in thermostats to help you maintain a constant temperature.
The major hazard associated with direct fired heaters is carbon-monoxide poisoning due to fuel combustion and poor ventilation of the space. These types of heaters cannot be used in small or tightly sealed spaces for this reason. Additionally, because you’re dealing with an open flame, take care when sweeping dust or sawdust that could catch fire near a direct fired heater.
Indirect Fired Heaters
An indirect fired heater is very similar to a direct fired unit in that it burns propane, natural gas, or diesel fuel to create heat. The main difference is what makes an indirect unit a better choice in terms of safety – the combustion takes place inside a burn chamber and releases the exhaust outdoors. This means the indoor air is safe to breathe for your employees and subcontractors. The air blown into the space is also dry which makes this a good option for dry out applications. The units are usually larger and placed outside with ducting used to bring the warm air into the space.
Temporary Heater Safety Tips
- Always read the instructions on the side of the heating unit, which will vary from unit to unit.
- Inspect units prior to use daily and never use a heater that appears to be damaged.
- Keep heaters away from any combustible material.
- Choose a heater size that’s appropriate for the square footage.
- Use heaters certified by a national testing laboratory.
- Propane tanks must be secured to prevent tip-over.
- Keep propane cylinders at least 10 feet away from the heater.
- Replacement LP gas cylinders in storage cannot be kept inside of buildings.
- Don’t use any below grade LPG or LP. Propane settles in low areas. For example, in a basement without an exit, any spark or flame could ignite the gas concentration to create a damaging explosion.
- When using direct fired heaters, install CO detectors in the area to monitor carbon monoxide buildup.
- In case of an emergency, place a fully charged and inspected fire extinguisher within 50 feet of an active unit.
- Never leave a heater running unattended. A fire watch is required for overnight activity.
- Turn off the heater and allow it to cool down before refueling.
- Turn off the gas supply when heaters are not in use.
- Keep gas lines and ducting out of walkways to avoid tripping hazards.
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DISCLAIMER: The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities, and should not be construed as legal advice or opinion. Readers with specific questions should refer to applicable standards or consult with a professional.