Using a half face respirator for the first time can feel a little overwhelming — especially when it comes to filters. What goes where? How often should they be changed? And how do you know you’re using them correctly?

This guide is here to make things simple. It’s designed for people who are new to the Sundström SR 100, as well as those who’ve used P3 respirators before but are new to the Sundström system. We’ll walk through how the filter system works, how to fit and replace the filters, and the small but important steps that help keep your respirator comfortable and effective.

Getting to know the Sundström SR 100 system

The Sundström SR 100 is a reusable half mask designed to protect the wearer from a wide range of airborne contaminants when used with the correct Sundström filters. This includes exposure to particles, micro-organisms, biochemical substances, and certain gases or vapours, or combinations of these — depending on the filter setup used.

The mask body is made from soft silicone and is designed to seal around the nose, mouth and chin for a secure yet comfortable fit. Inhaled air is drawn through the attached filter and into the mask, while exhaled air is released through dedicated exhalation valves. The adjustable head harness helps keep the respirator stable during use, even during longer or more physically demanding tasks.

When fitted with a P3 particle filter, the SR 100 is commonly used in environments with fine and hazardous dusts, including silica dust, construction dust, sanding particles, and other respirable airborne particles. This makes it suitable for many trade, industrial, and maintenance settings where higher-grade particle protection is required.

Compared to disposable P2 masks, the SR 100 offers a reusable system with replaceable filters and a more reliable face seal. While both P2 and P3 protection have their place, P3 filters provide a higher level of filtration — capturing at least 99.95% of airborne particles, compared to 94% for P2 masks — making them better suited to environments with finer or more hazardous dusts, such as silica.

One of the key advantages of the Sundström SR 100 is its modular filter system. In simple terms, this means the respirator is designed so that different filters and components can be attached, removed, and replaced individually, depending on the type of protection needed and the environment you’re working in.

Rather than relying on a single, disposable filter or mask, a modular system allows users to build the right level of protection by combining particle filters, gas filters, and pre-filters as required. Each component has its own role and service life, so only the part that’s worn or used up needs replacing — not the entire respirator.

This modular approach makes the SR 100 more flexible, cost-effective, and easier to maintain, especially for users who work across different tasks or environments where exposure risks can change.

How the filter system works

The Sundström SR 100 uses a modular filter system, which means different types of filters can be attached depending on the type of airborne hazard you’re working around. The mask itself stays the same — it’s the filter selection that determines what you’re protected against.

Sundström filters are generally grouped into particle filters, gas filters, and combined filters, each designed to address different types of airborne contaminants.

1. Particle filters

Particle filters are designed to protect against airborne particles only, such as dust, mist, smoke, and fine hazardous particles.

A common example is the Sundström SR 510, which provides high-level P3 particle filtration. When fitted, air is drawn through the filter media, where particles are physically trapped. As more particles are captured, breathing resistance gradually increases — this is a normal sign that the filter is doing its job and may need replacing.

2. Gas filters

Gas filters are designed to protect against specific gases and vapours, not particles. Each gas filter is made to absorb or adsorb certain contaminants, and protection continues only until the filter media becomes saturated. This is why gas filters are selected based on the type of gas or vapour present.

Gas filters are often identified by colour coding and labelling, which is why you may notice filters with different colours, such as yellow or multi-coloured bands.

3. Combined filters

In environments where both particles and gases/vapours are present — for example, spray painting — particle filters and gas filters must be used together as a combined setup. In this configuration, the particle filter is fitted onto the gas filter, allowing protection against both hazard types at the same time.

Where the pre-filter fits in

Regardless of filter type, a pre-filter such as the Sundström SR 221 can be added to the front of the system. The pre-filter is not a protective element on its own, but it helps stop larger nuisance particles from reaching the main filter, extending its service life and protecting it from handling damage.

How air flows through the system

When the respirator is worn correctly, inhaled air is drawn through the filter system before entering the mask. In a typical particle-filter setup, air first passes through the pre-filter, which captures larger particles, and then through the P3 particle filter, where fine and hazardous particles are trapped within the filter media.

Clean, filtered air is then inhaled into the mask, while exhaled air exits through the mask’s exhalation valves, helping reduce moisture buildup and heat inside the respirator.

As particles gradually collect in the filters, breathing resistance will slowly increase. This is a normal and expected part of how mechanical particle filters work and is often the clearest sign that the filter is reaching the end of its service life and may need maintenance or replacement.

How to fit and change filters on the Sundström SR 100 (Step-by-Step)

Correctly fitting the filter is essential for the respirator to work as intended. Take a moment to follow these steps carefully — especially if this is your first time using the system.

The Sundström SR 100 is designed to work with different filter types, depending on the airborne hazards present. While the attachment method is similar across filters, there are important differences depending on whether you are using particle filters, gas filters, or a combined setup.

Before you begin:

Always use genuine Sundström filters and parts
Check that the filter selected is correct for your task
Ensure the filter is within its use-by date and packaging has not been opened
Never modify filters or components, as this can reduce protection and invalidate approvals

1. Identify the filter type

Sundström filters can be identified by their colour and label, which indicate the type of protection they provide:

Particle filters – protect against airborne particles only
Gas filters – protect against specific gases and vapours only
Combined filters – protect against both particles and gases/vapours

Note:

A particle filter alone does not protect against gases.
A gas filter alone does not protect against particles.

2. Fit the filters

After choosing which filter you’re using for your specific task, for example, the Sundström SR 510 particle filter, fit the filter/combined filter in the mask so that the arrows on the filter point towards the user’s face. Ensure to check that the edge of the filter is in the internal groove of the filter mounting all around.

3. For combined filters (gas + particle)

In environments where both particles and gases/vapours are present (for example, spray painting), gas and particle filters must be combined.

To assemble a combined filter:

Insert the gas filter into the respirator
Place the particle filter on top of the gas filter
Squeeze firmly until the particle filter snaps into place
Gently pull to confirm the filters are properly connected

Important:

The particle filter always snaps onto the gas filter.
The gas filter is always the component inserted into the respirator.

5. Install the pre-filter SR 221

The Sundström SR 221 pre-filter is not a protective element and must never be used as primary protection or as a substitute for a particle filter.

Its purpose is to:

Prevent nuisance particles from reaching the main filter
Increase the service life of the primary filter
Protect the main filter from handling damage

The pre-filter is fitted into the pre-filter holder.

And then pressed onto the front of the main filter.

When should you replace the filters?

Knowing when to change your filters is just as important as fitting them correctly. Filters don’t last forever, and replacing them at the right time helps maintain protection, comfort, and hygiene.

Pre-filters — Sundström SR 221

Pre-filters are the first line of defence and do the “dirty work” by catching larger particles.

Replace when:

Daily, or every time the respirator is used
They look visibly dirty, clogged, or unhygienic

Because they’re inexpensive and easy to change, regular replacement helps protect and extend the life of the main filter.

Particle filters (e.g Sundström SR 510)

Particle filters trap fine and hazardous particles inside the filter media.

Replace when:

You notice increased breathing resistance (it feels harder to breathe)
As a general guide, every 2–4 weeks in typical use
(They may last longer in lighter, cleaner environments)
The filter becomes damaged, wet, contaminated, or unhygienic

Breathing resistance increasing is a normal sign the filter is doing its job — and a clear signal it’s time for a change.

Gas filters

Gas filters protect against specific gases and vapours and wear out differently from particle filters.

Replace when:

You can smell or taste the contaminant while wearing the respirator
The filter has reached its recommended service life
The filter has been opened and left unused for extended periods
The filter becomes damaged or contaminated

Unlike particle filters, gas filters may not show physical signs of wear. Replacement is based on exposure time and breakthrough, not breathing resistance.

Using the SR 100 safely and effectively

Using the Sundström SR 100 correctly comes down to three simple things: choosing the right filter, fitting it properly, and replacing it at the right time. The system is designed to be flexible and easy to maintain, but its effectiveness depends on regular checks and good habits.

When in doubt, always err on the side of changing filters sooner rather than later, and make sure you’re using genuine Sundström components for the best fit, performance, and safety.

February 06 2026, by Tatianna Gerard When to Replace Sundström SR 100 Respirator Filters (And How to Do It Properly)